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OCT Fused Fiber Optic Couplers


  • Designed and Tested for OCT Applications
  • 850 nm, 930 nm, 1064 nm, or 1300 nm Center Wavelength
  • ±100 nm Bandwidth with Flat Spectral Response
  • Available with 50:50, 75:25, 90:10, or 99:1 Coupling Ratio

TW850R5A2

850 nm, FC/APC Connectors
50:50 Coupling Ratio

TW1300R1A2

1300 nm, FC/APC Connectors
99:1 Coupling Ratio

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Each coupler is engraved with the item number, serial number, and coupling ratio for easy identification. When the white port on the left is used as the input, the coupling ratios listed below correspond to the ratio of the measured output power from the right white port to the red port.

Features

  • 850 nm, 930 nm, 1064 nm, or 1300 nm Center Wavelength
  • ±100 nm Bandwidth with Flat Spectral Response Across Specified Range
  • Coupling Ratios Available: 50:50, 75:25, 90:10, or 99:1
  • 1064 nm Couplers Available with 0.14 NA or 0.22 NA Fiber
  • Bidirectional Coupling (Either End Can Be Used as an Input)
  • 2.0 mm Narrow Key FC/APC Connectors
  • Individual Test Report Included with Each Coupler 
    (See the Coupler Verification Tab; Click for a 850, 9301064 (0.14 NA), 1064 (0.22 NA), or 1300 nm Sample Data Sheet)
  • Contact Us for Custom Fiber Lead Lengths, Coupling Ratios, and Connectors

Thorlabs' Wideband OCT Fiber Optic Couplers are designed for splitting and mixing optical signals with specific coupling ratios and are useful in many interferometry techniques. Our wideband couplers feature a broad spectral range with minimal spectral dependency, making these couplers ideal for integration into optical coherence tomography (OCT) systems. These polarization-independent, passive, 2x2 single mode couplers feature a ±100 nm spectral bandwidth and are available with center wavelengths of 850 nm, 930 nm, 1064 nm, or 1300 nm. Our 1064 nm wideband couplers are available with the choice of either 0.14 NA fiber (HI1060) or 0.22 NA fiber (HI1060 FLEX). The fiber leads from the coupler tube are terminated with 2.0 mm narrow key FC/APC connectors. Thorlabs provides an individual test report with each coupler. For details on our testing methods, please see the Coupler Verification tab. 

Webpage Features
 info icon Clicking this info icon below will open a window that contains detailed specifications and plots.

As seen in the image above to the right, these couplers have two fibers on each end and the coupler tube is engraved with the item number for easy identification. Because these couplers are bidirectional, either end can be used as the input (refer to the 2x2 Coupling Examples tab above). As an illustrative example, if light is input into the white port of the TW1064R1A2A coupler (99:1 coupling ratio), 99% of the transmitted light is coupled into the white port on the other side of the coupler while the other 1% is coupled into the red port. In this example, the second white port is referred to as the signal output port, and the red port is referred to as a tap output port.

Thorlabs offers a full selection of fiber optic couplers for other center wavelengths or with FC/PC connectors; please see our Fiber Optic Couplers guide for details. If a custom connector configuration is needed, same-day turnaround is possible for small orders if the order is placed before 12 PM EST. Please contact Tech Support for inquiries. 

Definition of 2x2 Fused Fiber Optic Coupler Specifications

This tab provides a brief explanation of how we determine several key specifications for our 2x2 couplers. The ports of the coupler are defined as shown in the coupler schematic below. In the sections below, the light is input into port 1. Port 3 and port 4 would then be considered the signal and tap outputs, respectively.

2x2 CouplerPicture

 

Excess Loss

Excess loss in dB is determined by the ratio of the total input power to the total output power:

Excess Loss

Pport1 is the input power at port 1 and Pport3+Pport4 is the total output power from ports 3 and 4, assuming no input power at port 2. All powers are expressed in mW.

 

Polarization Dependent Loss (PDL)

The polarization dependent loss is defined as the ratio of the maximum and minimum transmissions due to polarization states in couplers. This specification pertains only to couplers not designed for maintaining polarization. PDL is always specified in decibels (dB), and can be calculated with the following equation:

Polarization Dependent Loss Equation

where Pmax is the maximum power able to be transmitted through the coupler when scanning across all possible polarization states. Pmin is the minimum transmission across those same states.

 

Optical Return Loss (ORL) / Directivity

The directivity refers to the fraction of input light that exits the coupler through an input port (i.e., light exiting at port 2) instead of the intended output port. It can be calculated in units of dB using the following equation:

Directivity or Return Loss

where Pport1 and Pport2 are the optical powers (in mW) in port 1 and port 2, respectively. This output is the result of back reflection at the junction of the legs of the coupler and represents a loss in the total light output at ports 3 and 4. For a 50:50 coupler, the directivity is equal to the optical return loss (ORL).

 

Insertion Loss

The insertion loss is defined as the ratio of the input power to the output power at one of the output legs of the coupler (signal or tap). Insertion loss is always specified in decibels (dB). It is generally defined using the equation below:

Insertion Loss

where Pin and Pout are the input and output powers (in mW). For our 2x2 couplers, the insertion loss specification is provided for both signal and tap outputs; our specifications always list insertion loss for the signal output first. To define the insertion loss for a specific output (port 3 or port 4), the equation is rewritten as:

Insertion Loss

Insertion Loss

A similar equation can be used to define the insertion loss at port 2 for input at port 1. However, as seen above, this is already defined as the directivity of the coupler.

Insertion loss inherently includes both coupling (e.g., light transferred to the other output leg) and excess loss (e.g., light lost from the coupler) effects. The maximum allowed insertion loss for each output, signal and tap, are both specified. Because the insertion loss in each output is correlated to light coupled to the other output, no coupler will ever have the maximum insertion loss in both outputs simultaneously.

Calculating Insertion Loss using Power Expressed in dBm
Insertion loss can also be easily calculated with the power expressed in units of dBm. The equation below shows the relationship between power expressed in mW and dBm:

Conversion

Then, the insertion loss in dB can be calculated as follows:

Insertion Loss

 


Click to Enlarge

A graphical representation of the coupling ratio calculation.

Coupling Ratio

Insertion loss (in dB) is the ratio of the input power to the output power from each leg of the coupler as a function of wavelength. It captures both the coupling ratio and the excess loss. The coupling ratio is calculated from the measured insertion loss. Coupling ratio (in %) is the ratio of the optical power from each output port (A and B) to the sum of the total power of both output ports as a function of wavelength. It is not impacted by spectral features such as the water absorption region because both output legs are affected equally.

 


Click to Enlarge

A graphical representation of the Uniformity calculation.

Uniformity

The uniformity is also calculated from the measured insertion loss. Uniformity is the variation (in dB) of the insertion loss over the bandwidth. It is a measure of how evenly the insertion loss is distributed over the spectral range. The uniformity of Path A is the difference between the value of highest insertion loss and the solid red insertion loss curve (in the Insertion Plot above). The uniformity of Path B is the difference between the solid blue insertion loss curve and the value of lowest insertion loss.

Animated example of 90:10 splitting and 50:50 mixing.

General Coupling Examples

2x2 fused fiber optic couplers can split or mix light between two optical fibers with minimal loss and at a specified coupling ratio. Thorlabs' couplers are available from stock in one of four ratios: 50:50, 75:25, 90:10, or 99:1. All of our fused fiber optic couplers are bidirectional, meaning that all ports can be used as an input. The animation to the right shows several simple coupling examples. 

The terms "Signal Output" and "Tap Output" refer to the higher and lower power outputs, respectively. To illustrate this, if light is input into the white port of the TW1064R1A2A coupler (99:1 coupling ratio), 99% of the transmitted light is coupled into the white port on the other side of the coupler while the other 1% is coupled into the red port. In this example, the second white port is referred to as the signal output port, and the red port is referred to as a tap output port. For a 50:50 coupler, the signal and tap ports would have the same power output. 

In our couplers with a red housing, the signal always propagates from blue to red or white to white, while the tap always propagates from blue to white or white to red. For other couplers, please refer to the datasheet included with the coupler to determine signal and tap propagation paths. 

Coupling Ratio Insertion Loss (Signal) Insertion Loss (Tap)
90:10 0.6 dB 10.1 dB
50:50 3.2 dB 3.2 dB

Specific Coupling Examples

In the examples below, two 2x2 1300 nm Wideband Fiber Optic Couplers (50:50 and 90:10 coupling ratios) are used with input signals A and B. The table to the right lists typical insertion loss (signal and tap outputs) for each coupler. To calculate the power at any given output, subtract the insertion loss for the signal or tap output from the input power (in dBm).

Example 1: Splitting Light from a Single Input

For this example, the couplers are used to split light from a single input into the signal and tap outputs as indicated in the diagrams below. In the table below, the output ports are highlighted in green.

90:10 Coupling Ratio 50:50 Coupling Ratio
Port  Signal A Signal A
1 (Input) 10 dBm (10 mW) 10 dBm (10 mW)
2 (Not Used) - -
3 (Signal Output) 9.4 dBm (8.7 mW) 6.8 dBm (4.8 mW)
4 (Tap Output) -0.1 dBm (1.0 mW) 6.8 dBm (4.8 mW)
Click on the Diagram
for Power Distributions
at Each Port

Example 2: Mixing Two Signals from Two Inputs

In this example, the couplers are used to mix light from two inputs, designated Signal A and Signal B. The outputs contain a mixed signal composed of both Signal A and Signal B in ratios depending on the coupling ratio. All ports are indicated in the diagrams below. In the table below, the output ports are highlighted in green.

90:10 Coupling Ratio 50:50 Coupling Ratio
Port Signal A Signal B Signal A Signal B
1 (Input A) 5 dBm (3.2 mW) - 5 dBm (3.2 mW) -
2 (Input B) - 8 dBm (6.3 mW) - 8 dBm (6.3 mW)
3 (Output) 4.4 dBm (2.8 mW) -2.1 dBm (0.6 mW) 1.6 dBm (1.4 mW) 4.8 dBm (3.0 mW)
4 (Output) -5.1 dBm (0.3 mW) 7.4 dBm (5.5 mW) 1.6 dBm (1.4 mW) 4.8 dBm (3.0 mW)
Click on the Diagram
for Power Distributions
at Each Port

Example 3: Coupling a Return Signal with a Reflector on Port 4

Here, the couplers are used to split light from a single input, however, in this example there is a 100% reflector on port 4, as shown in the diagrams below. As a result, the light is reflected back into the coupler and split again. The ports are indicated in the diagrams below. In the table below, the output ports for the initial pass are highlighted in green.

90:10 Coupling Ratio 50:50 Coupling Ratio
Port Signal A Reflected Signal A Signal A Reflected Signal A
1 (Input) 6 dBm (4.0 mW) -14.2 dBm (0.04 mW) 6 dBm (4.0 mW) -0.4 dBm (0.9 mW)
2 (No Input) - -4.7 dBm (0.34 mW) - -0.4 dBm (0.9 mW)
3 (Signal Output) 5.4 dBm (3.5 mW) - 2.8 dBm (1.9 mW) -
4 (Reflected Output) -4.1 dBm (0.39 mW) Reflected - 2.8 dBm (1.9 mW) Reflected -
Click on the Diagram
for Power Distributions
at Each Port

Wideband Fiber Coupler Testing and Verification Procedure

During Thorlabs' coupling manufacturing process, the coupling ratio and bandwidth of each wideband coupler is monitored as the two branches are fused together. This ensures that each coupler meets the stated specifications over the bandwidth. Each wideband coupler is shipped with an individualized data sheet providing a summary of the results of these tests. Click for a 850, 1064 (0.14 NA), 1064 (0.22 NA), or 1300 nm sample data sheet.

Step 1

The fiber to create the first branch (Path A) of the coupler is connected to a source on one side and a switch leading to an Optical Spectrum Analyzer (OSA) on the other.


Step 2

The spectrum of the source through the fiber and switch is measured using the OSA and zeroed. 


Step 3

The fiber to form the second branch (Path B) of the coupler is connected to the source and to the second port of the switch leading to the OSA. The spectrum of the source through the fiber and switch is also measured and zeroed.


Step 4

The two fibers are fused on a manufacturing station to create the coupler structure. During the fusing process, the output from both legs of the coupler is monitored on the OSA. Coupler fusing stops once the coupler reaches the desired coupling ratio, excess loss, and insertion loss specifications.

For 1x2 couplers, one of the fiber ends is terminated within the coupler housing. The termination is done in a manner that minimizes back reflections from this output.



Click to Enlarge

Insertion loss (in dB) is the ratio of the input power to the output power from each leg of the coupler as a function of wavelength. It captures both the coupling ratio and the excess loss. The coupling ratio is calculated from the measured insertion loss. Coupling ratio (in %) is the ratio of the optical power from each output port (A and B) to the sum of the total power of both output ports as a function of wavelength. It is not impacted by spectral features such as the water absorption region because both output legs are affected equally. Persistence plots showing the coupling ratio of our wideband couplers can be viewed by clicking on the blue info icons below.

Click to Enlarge

The uniformity is also calculated from the measured insertion loss. Uniformity is the variation (in dB) of the insertion loss over the bandwidth. It is a measure of how evenly the insertion loss is distributed over the spectral range. The uniformity of Path A is the difference between the value of highest insertion loss and the solid red insertion loss curve (in the Insertion Plot above). The uniformity of Path B is the difference between the solid blue insertion loss curve and the value of lowest insertion loss. Persistence plots showing the uniformity of our wideband couplers can be viewed by clicking on the blue info icons below.

Laser-Induced Damage in Silica Optical Fibers

The following tutorial details damage mechanisms relevant to unterminated (bare) fiber, terminated optical fiber, and other fiber components from laser light sources. These mechanisms include damage that occurs at the air / glass interface (when free-space coupling or when using connectors) and in the optical fiber itself. A fiber component, such as a bare fiber, patch cable, or fused coupler, may have multiple potential avenues for damage (e.g., connectors, fiber end faces, and the device itself). The maximum power that a fiber can handle will always be limited by the lowest limit of any of these damage mechanisms.

While the damage threshold can be estimated using scaling relations and general rules, absolute damage thresholds in optical fibers are very application dependent and user specific. Users can use this guide to estimate a safe power level that minimizes the risk of damage. Following all appropriate preparation and handling guidelines, users should be able to operate a fiber component up to the specified maximum power level; if no maximum is specified for a component, users should abide by the "practical safe level" described below for safe operation of the component. Factors that can reduce power handling and cause damage to a fiber component include, but are not limited to, misalignment during fiber coupling, contamination of the fiber end face, or imperfections in the fiber itself. For further discussion about an optical fiber’s power handling abilities for a specific application, please contact Thorlabs’ Tech Support.

Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Undamaged Fiber End
Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Damaged Fiber End

Damage at the Air / Glass Interface

There are several potential damage mechanisms that can occur at the air / glass interface. Light is incident on this interface when free-space coupling or when two fibers are mated using optical connectors. High-intensity light can damage the end face leading to reduced power handling and permanent damage to the fiber. For fibers terminated with optical connectors where the connectors are fixed to the fiber ends using epoxy, the heat generated by high-intensity light can burn the epoxy and leave residues on the fiber facet directly in the beam path.

Estimated Optical Power Densities on Air / Glass Interfacea
Type Theoretical Damage Thresholdb Practical Safe Levelc
CW
(Average Power)
~1 MW/cm2 ~250 kW/cm2
10 ns Pulsed
(Peak Power)
~5 GW/cm2 ~1 GW/cm2
  • All values are specified for unterminated (bare) silica fiber and apply for free space coupling into a clean fiber end face.
  • This is an estimated maximum power density that can be incident on a fiber end face without risking damage. Verification of the performance and reliability of fiber components in the system before operating at high power must be done by the user, as it is highly system dependent.
  • This is the estimated safe optical power density that can be incident on a fiber end face without damaging the fiber under most operating conditions.

Damage Mechanisms on the Bare Fiber End Face

Damage mechanisms on a fiber end face can be modeled similarly to bulk optics, and industry-standard damage thresholds for UV Fused Silica substrates can be applied to silica-based fiber. However, unlike bulk optics, the relevant surface areas and beam diameters involved at the air / glass interface of an optical fiber are very small, particularly for coupling into single mode (SM) fiber. therefore, for a given power density, the power incident on the fiber needs to be lower for a smaller beam diameter.

The table to the right lists two thresholds for optical power densities: a theoretical damage threshold and a "practical safe level". In general, the theoretical damage threshold represents the estimated maximum power density that can be incident on the fiber end face without risking damage with very good fiber end face and coupling conditions. The "practical safe level" power density represents minimal risk of fiber damage. Operating a fiber or component beyond the practical safe level is possible, but users must follow the appropriate handling instructions and verify performance at low powers prior to use.

Calculating the Effective Area for Single Mode and Multimode Fibers
The effective area for single mode (SM) fiber is defined by the mode field diameter (MFD), which is the cross-sectional area through which light propagates in the fiber; this area includes the fiber core and also a portion of the cladding. To achieve good efficiency when coupling into a single mode fiber, the diameter of the input beam must match the MFD of the fiber.

As an example, SM400 single mode fiber has a mode field diameter (MFD) of ~Ø3 µm operating at 400 nm, while the MFD for SMF-28 Ultra single mode fiber operating at 1550 nm is Ø10.5 µm. The effective area for these fibers can be calculated as follows:

SM400 Fiber: Area = Pi x (MFD/2)2 = Pi x (1.5 µm)2 = 7.07 µm= 7.07 x 10-8 cm2

 SMF-28 Ultra Fiber: Area = Pi x (MFD/2)2 = Pi x (5.25 µm)2 = 86.6 µm= 8.66 x 10-7 cm2

To estimate the power level that a fiber facet can handle, the power density is multiplied by the effective area. Please note that this calculation assumes a uniform intensity profile, but most laser beams exhibit a Gaussian-like shape within single mode fiber, resulting in a higher power density at the center of the beam compared to the edges. Therefore, these calculations will slightly overestimate the power corresponding to the damage threshold or the practical safe level. Using the estimated power densities assuming a CW light source, we can determine the corresponding power levels as:

SM400 Fiber: 7.07 x 10-8 cm2 x 1 MW/cm2 = 7.1 x 10-8 MW = 71 mW (Theoretical Damage Threshold)
     7.07 x 10-8 cm2 x 250 kW/cm2 = 1.8 x 10-5 kW = 18 mW (Practical Safe Level)

SMF-28 Ultra Fiber: 8.66 x 10-7 cm2 x 1 MW/cm2 = 8.7 x 10-7 MW = 870 mW (Theoretical Damage Threshold)
           8.66 x 10-7 cm2 x 250 kW/cm2 = 2.1 x 10-4 kW = 210 mW (Practical Safe Level)

The effective area of a multimode (MM) fiber is defined by the core diameter, which is typically far larger than the MFD of an SM fiber. For optimal coupling, Thorlabs recommends focusing a beam to a spot roughly 70 - 80% of the core diameter. The larger effective area of MM fibers lowers the power density on the fiber end face, allowing higher optical powers (typically on the order of kilowatts) to be coupled into multimode fiber without damage.

Damage Mechanisms Related to Ferrule / Connector Termination


Click to Enlarge
Plot showing approximate power handling levels for single mode silica optical fiber with a termination. Each line shows the estimated power level due to a specific damage mechanism. The maximum power handling is limited by the lowest power level from all relevant damage mechanisms (indicated by a solid line).

Fibers terminated with optical connectors have additional power handling considerations. Fiber is typically terminated using epoxy to bond the fiber to a ceramic or steel ferrule. When light is coupled into the fiber through a connector, light that does not enter the core and propagate down the fiber is scattered into the outer layers of the fiber, into the ferrule, and the epoxy used to hold the fiber in the ferrule. If the light is intense enough, it can burn the epoxy, causing it to vaporize and deposit a residue on the face of the connector. This results in localized absorption sites on the fiber end face that reduce coupling efficiency and increase scattering, causing further damage.

For several reasons, epoxy-related damage is dependent on the wavelength. In general, light scatters more strongly at short wavelengths than at longer wavelengths. Misalignment when coupling is also more likely due to the small MFD of short-wavelength SM fiber that also produces more scattered light.

To minimize the risk of burning the epoxy, fiber connectors can be constructed to have an epoxy-free air gap between the optical fiber and ferrule near the fiber end face. Our high-power multimode fiber patch cables use connectors with this design feature.

Determining Power Handling with Multiple Damage Mechanisms

When fiber cables or components have multiple avenues for damage (e.g., fiber patch cables), the maximum power handling is always limited by the lowest damage threshold that is relevant to the fiber component.

As an illustrative example, the graph to the right shows an estimate of the power handling limitations of a single mode fiber patch cable due to damage to the fiber end face and damage via an optical connector. The total power handling of a terminated fiber at a given wavelength is limited by the lower of the two limitations at any given wavelength (indicated by the solid lines). A single mode fiber operating at around 488 nm is primarily limited by damage to the fiber end face (blue solid line), but fibers operating at 1550 nm are limited by damage to the optical connector (red solid line).

In the case of a multimode fiber, the effective mode area is defined by the core diameter, which is larger than the effective mode area for SM fiber. This results in a lower power density on the fiber end face and allows higher optical powers (on the order of kilowatts) to be coupled into the fiber without damage (not shown in graph). However, the damage limit of the ferrule / connector termination remains unchanged and as a result, the maximum power handling for a multimode fiber is limited by the ferrule and connector termination. 

Please note that these are rough estimates of power levels where damage is very unlikely with proper handling and alignment procedures. It is worth noting that optical fibers are frequently used at power levels above those described here. However, these applications typically require expert users and testing at lower powers first to minimize risk of damage. Even still, optical fiber components should be considered a consumable lab supply if used at high power levels.

Intrinsic Damage Threshold

In addition to damage mechanisms at the air / glass interface, optical fibers also display power handling limitations due to damage mechanisms within the optical fiber itself. These limitations will affect all fiber components as they are intrinsic to the fiber itself. Two categories of damage within the fiber are damage from bend losses and damage from photodarkening. 

Bend Losses
Bend losses occur when a fiber is bent to a point where light traveling in the core is incident on the core/cladding interface at an angle higher than the critical angle, making total internal reflection impossible. Under these circumstances, light escapes the fiber, often in a localized area. The light escaping the fiber typically has a high power density, which burns the fiber coating as well as any surrounding furcation tubing.

A special category of optical fiber, called double-clad fiber, can reduce the risk of bend-loss damage by allowing the fiber’s cladding (2nd layer) to also function as a waveguide in addition to the core. By making the critical angle of the cladding/coating interface higher than the critical angle of the core/clad interface, light that escapes the core is loosely confined within the cladding. It will then leak out over a distance of centimeters or meters instead of at one localized spot within the fiber, minimizing the risk of damage. Thorlabs manufactures and sells 0.22 NA double-clad multimode fiber, which boasts very high, megawatt range power handling.

Photodarkening
A second damage mechanism, called photodarkening or solarization, can occur in fibers used with ultraviolet or short-wavelength visible light, particularly those with germanium-doped cores. Fibers used at these wavelengths will experience increased attenuation over time. The mechanism that causes photodarkening is largely unknown, but several fiber designs have been developed to mitigate it. For example, fibers with a very low hydroxyl ion (OH) content have been found to resist photodarkening and using other dopants, such as fluorine, can also reduce photodarkening.

Even with the above strategies in place, all fibers eventually experience photodarkening when used with UV or short-wavelength light, and thus, fibers used at these wavelengths should be considered consumables.

Preparation and Handling of Optical Fibers

General Cleaning and Operation Guidelines
These general cleaning and operation guidelines are recommended for all fiber optic products. Users should still follow specific guidelines for an individual product as outlined in the support documentation or manual. Damage threshold calculations only apply when all appropriate cleaning and handling procedures are followed.

  1. All light sources should be turned off prior to installing or integrating optical fibers (terminated or bare). This ensures that focused beams of light are not incident on fragile parts of the connector or fiber, which can possibly cause damage.

  2. The power-handling capability of an optical fiber is directly linked to the quality of the fiber/connector end face. Always inspect the fiber end prior to connecting the fiber to an optical system. The fiber end face should be clean and clear of dirt and other contaminants that can cause scattering of coupled light. Bare fiber should be cleaved prior to use and users should inspect the fiber end to ensure a good quality cleave is achieved.

  3. If an optical fiber is to be spliced into the optical system, users should first verify that the splice is of good quality at a low optical power prior to high-power use. Poor splice quality may increase light scattering at the splice interface, which can be a source of fiber damage.

  4. Users should use low power when aligning the system and optimizing coupling; this minimizes exposure of other parts of the fiber (other than the core) to light. Damage from scattered light can occur if a high power beam is focused on the cladding, coating, or connector.

Tips for Using Fiber at Higher Optical Power
Optical fibers and fiber components should generally be operated within safe power level limits, but under ideal conditions (very good optical alignment and very clean optical end faces), the power handling of a fiber component may be increased. Users must verify the performance and stability of a fiber component within their system prior to increasing input or output power and follow all necessary safety and operation instructions. The tips below are useful suggestions when considering increasing optical power in an optical fiber or component.

  1. Splicing a fiber component into a system using a fiber splicer can increase power handling as it minimizes possibility of air/fiber interface damage. Users should follow all appropriate guidelines to prepare and make a high-quality fiber splice. Poor splices can lead to scattering or regions of highly localized heat at the splice interface that can damage the fiber.

  2. After connecting the fiber or component, the system should be tested and aligned using a light source at low power. The system power can be ramped up slowly to the desired output power while periodically verifying all components are properly aligned and that coupling efficiency is not changing with respect to optical launch power.

  3. Bend losses that result from sharply bending a fiber can cause light to leak from the fiber in the stressed area. When operating at high power, the localized heating that can occur when a large amount of light escapes a small localized area (the stressed region) can damage the fiber. Avoid disturbing or accidently bending fibers during operation to minimize bend losses.

  4. Users should always choose the appropriate optical fiber for a given application. For example, large-mode-area fibers are a good alternative to standard single mode fibers in high-power applications as they provide good beam quality with a larger MFD, decreasing the power density on the air/fiber interface.

  5. Step-index silica single mode fibers are normally not used for ultraviolet light or high-peak-power pulsed applications due to the high spatial power densities associated with these applications.


Posted Comments:
bdada  (posted 2012-06-01 11:51:00.0)
Response from Buki at Thorlabs to xj.gong: As a follow up to my initial post, we have confirmed the phase shift to be 90 degrees.
bdada  (posted 2012-05-17 16:30:00.0)
Response from Buki at Thorlabs: Thank you for your feedback. We will measure the phase shift and send you the information.
xj.gong  (posted 2012-05-17 01:23:50.0)
Hi, it is my first time to use the fiber coupler. Could you tell me whethter the light at each output port have phase difference of 90 degree? Thank you!
bdada  (posted 2012-01-05 13:49:00.0)
Response from Buki at Thorlabs: In about a month, the SM800 fiber used in the FC850-40-50-APC coupler will be replaced with 780HP fiber. We will contact you with more information. Please contact TechSupport@thorlabs.com if you have any questions.
kyelee4  (posted 2012-01-04 14:38:26.0)
Hi, Can you provide the boadband fiber coupler using fiber 780HP instead of SM800? Thanks,
apalmentieri  (posted 2010-01-21 19:27:52.0)
A response from Adam at Thorlabs to p.langehanenberg: The ratio is relative. For example, light input into lead A1 of the FC850-40-01-APC coupler will be split so that 99% of the transmitted light is coupled into the B2 lead while the other 1% is coupled into the B1 lead. The coupler is bidirectional, in that you can input the light into any of the fiber leads and have the transmitted light split between the two leads in the other lead pair. Please note that if light is coupled into A2, then 99% of the light is coupled into the B1 lead and 1% is coupled into the B2 lead.
p.langehanenberg  (posted 2010-01-21 18:07:54.0)
Dear Sir or Madam, I hope you can help me with a technical question: in case of uneven beam ratios (e.g., 90:10), is this ratio relative (as it is in optical beam splitter cubes) or is it absolute? By absolute I mean that one arm is always the weak and one the intense one, no matter, which fiber is used in the opposite side of the coupler. Thank you very much for your quick response. Kind regards, Patrik Langehanenberg Trioptics GmbH Wedel, Germany

850 nm OCT Wideband Fiber Optic Couplers, 2x2

Item # Info  Coupling
Ratio (%)a
(Click for Plot)
Coupling Ratio Tolerance (%) Minimum Bandwidthb Excess Lossa,c Insertion Lossa,c Uniformitya
(Click for Plot)
Directivitya,c Fiber Typed Cut-Off Wavelengthb
TW850R5A2 info 50:50 ±6.0% ±100 nm ≤0.3 dB ≤3.9 dB / ≤3.9 dB ≤1.0 dB ≥60 dB 780HP 730 ± 30 nm
TW850R3A2 info 75:25 ±3.75% ≤1.8 dB / ≤7.0 dB ≤1.25 dB
TW850R2A2 info 90:10 ±3.0% ≤0.9 dB / ≤11.8 dB ≤2.0 dB
TW850R1A2 info 99:1 ±0.6% ≤0.4 dB / ≤24.3 dB ≤3.0 dB
  • All values are specified at room temperature over the bandwidth without connectors and measured using the white port as the input, as indicated in the diagram above; similar performance is achieved (≤0.05 dB difference) when the blue port is used as the input.
  • Below the cut-off wavelength, single mode operation is not guaranteed.
  • Please see the 2x2 Coupler Tutorial tab for more information on these terms.
  • Other fiber types may be available upon request. Please contact Tech Support with inquiries.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
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TW850R5A2 Support Documentation
TW850R5A22x2 Wideband Fiber Optic Coupler, 850 ± 100 nm, 50:50 Split, FC/APC
$364.14
Today
TW850R3A2 Support Documentation
TW850R3A22x2 Wideband Fiber Optic Coupler, 850 ± 100 nm, 75:25 Split, FC/APC
$364.14
Today
TW850R2A2 Support Documentation
TW850R2A22x2 Wideband Fiber Optic Coupler, 850 ± 100 nm, 90:10 Split, FC/APC
$364.14
Today
TW850R1A2 Support Documentation
TW850R1A22x2 Wideband Fiber Optic Coupler, 850 ± 100 nm, 99:1 Split, FC/APC
$364.14
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930 nm OCT Wideband Fiber Optic Couplers, 2x2

Item # Info  Coupling
Ratio (%)a
(Click for Plot)
Coupling Ratio Tolerance (%) Minimum Bandwidth Excess Lossa,b Insertion Lossa,b Uniformitya
(Click for Plot)
Directivitya,b Fiber Typec Cut-Off Wavelength
TW930R5A2 info 50:50 ±6.0% ±100 nm ≤0.3 dB ≤3.9 dB / ≤3.9 dB ≤1.0 dB ≥60 dB 780HP 730 ± 30 nm
TW930R3A2 info 75:25 ±3.75% ≤1.8 dB / ≤7.0 dB ≤1.25 dB
TW930R2A2 info 90:10 ±3.0% ≤0.9 dB / ≤11.8 dB ≤2.0 dB
TW930R1A2 info 99:1 ±0.6% ≤0.4 dB / ≤24.3 dB ≤3.0 dB
  • All values are specified at room temperature over the bandwidth without connectors and measured using the white port as the input, as indicated in the diagram above; similar performance is achieved (≤0.05 dB difference) when the blue port is used as the input.
  • Please see the 2x2 Coupler Tutorial tab for more information on these terms.
  • Other fiber types may be available upon request. Please contact Tech Support with inquiries.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
TW930R5A2 Support Documentation
TW930R5A22x2 Wideband Fiber Optic Coupler, 930 ± 100 nm, 50:50 Split, FC/APC
$364.14
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TW930R3A2 Support Documentation
TW930R3A22x2 Wideband Fiber Optic Coupler, 930 ± 100 nm, 75:25 Split, FC/APC
$364.14
Today
TW930R2A2 Support Documentation
TW930R2A22x2 Wideband Fiber Optic Coupler, 930 ± 100 nm, 90:10 Split, FC/APC
$364.14
Today
TW930R1A2 Support Documentation
TW930R1A22x2 Wideband Fiber Optic Coupler, 930 ± 100 nm, 99:1 Split, FC/APC
$364.14
Today

1064 nm, 0.14 NA, OCT Wideband Fiber Optic Couplers, 2x2

Item # Info  Coupling Ratio (%)a
(Click for Plot)
Coupling Ratio Tolerance (%) Minimum Bandwidthb Excess Lossa,c Insertion Lossa,c Uniformitya
(Click for Plot)
Directivitya,c Fiber Typed Cut-Off Wavelengthb
TW1064R5A2A info 50:50 ±5.0% ±100 nm ≤0.2 dB ≤3.7 dB / ≤3.7 dB ≤0.5 dB ≥60 dB HI1060
(0.14 NA)
920 ± 50 nm
TW1064R3A2A info 75:25 ±3.5% ≤1.7 dB / ≤6.9 dB ≤0.6 dB
TW1064R2A2A info 90:10 ±2.5% ≤0.8 dB / ≤11.4 dB ≤0.6 dB
TW1064R1A2A info 99:1 ±0.6% ≤0.3 dB / ≤24.2 dB ≤1.0 dB
  • All values are specified at room temperature over the bandwidth without connectors and measured using the white port as the input, as indicated in the diagram above; similar performance is achieved (≤0.05 dB difference) when the blue port is used as the input.
  • Below the cut-off wavelength, single mode operation is not guaranteed.
  • Please see the 2x2 Coupler Tutorial tab for more information on these terms.
  • Other fiber types may be available upon request. Please contact Tech Support with inquiries.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
TW1064R5A2A Support Documentation
TW1064R5A2A2x2 Wideband Fiber Optic Coupler, 1064 ± 100 nm, 0.14 NA, 50:50 Split, FC/APC
$364.14
Today
TW1064R3A2A Support Documentation
TW1064R3A2A2x2 Wideband Fiber Optic Coupler, 1064 ± 100 nm, 0.14 NA, 75:25 Split, FC/APC
$364.14
Today
TW1064R2A2A Support Documentation
TW1064R2A2A2x2 Wideband Fiber Optic Coupler, 1064 ± 100 nm, 0.14 NA, 90:10 Split, FC/APC
$364.14
Today
TW1064R1A2A Support Documentation
TW1064R1A2A2x2 Wideband Fiber Optic Coupler, 1064 ± 100 nm, 0.14 NA, 99:1 Split, FC/APC
$364.14
Today

1064 nm, 0.22 NA, OCT Wideband Fiber Optic Couplers, 2x2

Item # Info  Coupling Ratio (%)a
(Click for Plot)
Coupling Ratio Tolerance (%) Minimum Bandwidthb Excess Lossa,c Insertion Lossa,c Uniformitya
(Click for Plot)
Directivitya,c Fiber Typed Cut-Off Wavelengthb
TW1064R5A2B info 50:50 ±5.0% ±100 nm ≤0.2 dB ≤3.7 dB / ≤3.7 dB ≤0.5 dB ≥60 dB HI1060 FLEX
(0.22 NA)
930 ± 40 nm
TW1064R3A2B info 75:25 ±3.5% ≤1.7 dB / ≤6.9 dB ≤0.6 dB
TW1064R2A2B info 90:10 ±2.5% ≤0.8 dB / ≤11.4 dB ≤0.7 dB
TW1064R1A2B info 99:1 ±0.6% ≤0.3 dB / ≤24.2 dB ≤1.0 dB
  • All values are specified at room temperature over the bandwidth without connectors and measured using the white port as the input, as indicated in the diagram above; similar performance is achieved (≤0.05 dB difference) when the blue port is used as the input.
  • Below the cut-off wavelength, single mode operation is not guaranteed.
  • Please see the 2x2 Coupler Tutorial tab for more information on these terms.
  • Other fiber types may be available upon request. Please contact Tech Support with inquiries.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
TW1064R5A2B Support Documentation
TW1064R5A2B2x2 Wideband Fiber Optic Coupler, 1064 ± 100 nm, 0.22 NA, 50:50 Split, FC/APC
$364.14
Today
TW1064R3A2B Support Documentation
TW1064R3A2B2x2 Wideband Fiber Optic Coupler, 1064 ± 100 nm, 0.22 NA, 75:25 Split, FC/APC
$364.14
Today
TW1064R2A2B Support Documentation
TW1064R2A2B2x2 Wideband Fiber Optic Coupler, 1064 ± 100 nm, 0.22 NA, 90:10 Split, FC/APC
$364.14
Today
TW1064R1A2B Support Documentation
TW1064R1A2B2x2 Wideband Fiber Optic Coupler, 1064 ± 100 nm, 0.22 NA, 99:1 Split, FC/APC
$364.14
Today

1300 nm OCT Wideband Fiber Optic Couplers, 2x2

Item # Info  Coupling Ratio (%)a
(Click for Plot)
Coupling Ratio Tolerance (%) Minimum Bandwidthb Excess Lossa,c,d Insertion Lossa,c,d Uniformitya,d
(Click for Plot)
Directivitya,c Fiber Typee Cut-Off Wavelengthb
TW1300R5A2 info 50:50 ±5.0% ±100 nm ≤0.15 dB ≤3.6 dB / ≤3.6 dB ≤0.5 dB ≥60 dB SMF-28e+ ≤1260 nm
TW1300R3A2 info 75:25 ±3.5% ≤1.6 dB / ≤6.8 dB ≤0.6 dB
TW1300R2A2 info 90:10 ±2.50% ≤0.7 dB / ≤11.4 dB ≤0.6 dB
TW1300R1A2 info 99:1 ±0.6% ≤0.2 dB / ≤24.1 dB ≤0.8 dB
  • All values are specified at room temperature over the bandwidth without connectors and measured using the white port as the input, as indicated in the diagram above; similar performance is achieved (≤0.05 dB difference) when the blue port is used as the input.
  • Below the cut-off wavelength, single mode operation is not guaranteed.
  • Please see the 2x2 Coupler Tutorial tab for more information on these terms.
  • This specification excludes the water absorption region centered around 1383 nm. For more details, please click on the blue info icons in the table above.
  • Other fiber types may be available upon request. Please contact Tech Support with inquiries.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
TW1300R5A2 Support Documentation
TW1300R5A22x2 Wideband Fiber Optic Coupler, 1300 ± 100 nm, 50:50 Split, FC/APC
$364.14
Today
TW1300R3A2 Support Documentation
TW1300R3A22x2 Wideband Fiber Optic Coupler, 1300 ± 100 nm, 75:25 Split, FC/APC
$364.14
Today
TW1300R2A2 Support Documentation
TW1300R2A22x2 Wideband Fiber Optic Coupler, 1300 ± 100 nm, 90:10 Split, FC/APC
$364.14
Today
TW1300R1A2 Support Documentation
TW1300R1A22x2 Wideband Fiber Optic Coupler, 1300 ± 100 nm, 99:1 Split, FC/APC
$364.14
Today
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