Dual-Core Multimode Fiber Patch Cables for Optogenetics
- Dual-Core Fiber Patch Cables for Optogenetics
- Ideal for Bilateral Stimulation or Silencing
- Ø2.5 mm Dual-Core Stainless Steel Ferrule
- FC/PC or SMA905 Connectors on Split Ends
Dual-Core Patch Cable with FC/PC
Connectors on Split Ends and Ø2.5 mm
Stainless Steel Ferrule on Common End
Dual-Core Patch Cables Enable Light at Different Wavelengths to be Inserted in Close Proximity
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Dual-Core Optogenetics Patch Cables are Designed to Work with our Dual-Core Implantable Dual-Core Cannulas
- Dual-Core Fiber Patch Cables for Bilateral Stimulation or Silencing
- Common End: Ø2.5 mm Stainless Steel Ferrule with
700 µm Core Spacing
- Split Ends: FC/PC or SMA905 Connectors
- Common End: Ø2.5 mm Stainless Steel Ferrule with
- Two Ø200 µm Core, 0.39 NA Multimode Fibers
- Compatible with Our Dual-Core Fiber Optic Cannulae
- Lightweight Protective Tubing
- Contact Tech Support for Custom Fiber Lengths, Fiber Type, or Core Separation Distance
The dual-core multimode fiber optic patch cables sold on this page are specifically designed to be used with our implantable dual-core fiber optic cannulae. Thorlabs' dual-core products allow high-intensity light from two different sources to be implanted within a specimen in close proximity (~1 mm), and are therefore ideal for applications such as bilateral stimulation or silencing.
These dual-core patch cables feature two Ø200 µm core, 0.39 NA fibers combined into a Ø2.5 mm common-end stainless steel ferrule with a 700 µm core spacing (see the image to the right). The split ends of the patch cable have either SMA905 or 2.0 mm narrow key FC/PC connectors for connection to our fiber-coupled LEDs or lasers, respectively. The fiber is encased within a thin, approximately Ø1.4 mm outer tubing to both protect the fiber and minimize cable mass, reducing stress on a living specimen.
For ease of use and alignment, the common-end ferrule is equipped with a Ø0.03" (Ø0.8 mm) mating pin which fits into a matching guide hole in our dual-core cannulae. When used with the ADAF1 mating sleeve (shown in animation) or the ADAF2 interconnect, the mating pin and guide hole ensure precise alignment of the two fiber cores. The ferrule is engraved with an alignment mark that corresponds to a matching engraving on our dual-core fiber patch cables (see the image to the above). For more details on the usage of the dual-core patch cable and cannula, please see the Usage Tips tab above.
Each patch cable includes three protective caps that shield the ferrule ends from dust and other hazards when not in use. Additional caps such as the CAPF Plastic Caps (compatible with the ferrule and FC/PC ends), CAPFM (compatible only with FC/PC connectors), CAPM (compatible with SMA905 connectors), and CAPSM (compatible with SMA905 connectors) are sold separately. If the ferrule or fiber ends become dirty from use, we offer a selection of inspection tools and fiber optic cleaning products.
Thorlabs' line of single-core optogenetics patch cables are available from stock with either Ø1.25 mm or Ø2.5 mm ceramic ferrules and fiber core sizes from Ø200 µm to Ø400 µm, and with an NA of 0.22 or 0.39. These options provide experimental flexibility for working with in vitro or in vivo specimens. Custom options are also available for our dual-core patch cables; contact Tech Support for details.
Optogenetics Product Family for In Vivo Applications
The image below illustrates an example dual-core optogenetics system. Thorlabs offers a wide variety of products designed to support in vivo optogenetics applications. Please visit the OG Selection Guide tab above to see a full listing of available products for different applications.
This tab contains instructions for assembling and disassembling a dual-core fiber optic patch cable and cannula. The animation to the right illustrates the assembly process using a dual-core patch cable, ADAF1 lightweight mating sleeve, and dual-core cannula. The ADAF2 Quick-Release Interconnect, which provides lower-force connections than the ADAF1 mating sleeve, can be found here.
Connecting the Patch Cable and Cannula
Insert the patch cable ferrule approximately halfway into the Ø2.5 mm mating sleeve (Item # ADAF1). The ferrule should fit tightly within the mating sleeve. Then, insert the cannula ferrule into the mating sleeve from the other side.
- Ensure that the patch cable and cannula ferrule tips are clean and free of dust; we recommend our canned compressed air.
- If the two ferrules are properly aligned, the engraved markings on each ferrule should be aligned; if not, rotate the cannula until the engravings align.
Once aligned, gently press the two ferrules together until contact is achieved. Do not try to force the two ferrules together; if the alignment pin is misaligned, this may damage the ferrule.
Disconnecting the Patch Cable and Cannula
For best results when disconnecting the cable and cannula, hold the patch cable near the jacket/ferrule interface and gently pull the ferrule from the ADAF1 mating sleeve.
|Damage at the Air / Glass Interface|
|Intrinsic Damage Threshold|
|Preparation and Handling of Optical Fibers|
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.
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Undamaged Fiber End
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Damaged Fiber End
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|
|~1 MW/cm2||~250 kW/cm2|
|10 ns Pulsed
|~5 GW/cm2||~1 GW/cm2|
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 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 µm2 = 7.07 x 10-8 cm2
SMF-28 Ultra Fiber: Area = Pi x (MFD/2)2 = Pi x (5.25 µm)2 = 86.6 µm2 = 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)
Effective Area of Multimode Fibers
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
Plot showing approximate input power that can be incident on a 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. In general, this represents the highest input power that can be incident on the patch cable end face and not the coupled output power.
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 input 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.
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 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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|One Light Source to One Cannula Implant|
|One Light Source to Two Cannula Implants Using Rotary Joint Splitter|
|One or Two Light Sources to Two Cannula Implants|
|Two Light Sources into One Dual-Core Cannula Implant|
|Fiber-Coupled LEDs and Drivers|
Optogenetics Selection Guide
Thorlabs offers a wide range of optogenetics components; the compatibility of these products in select standard configurations is discussed in detail here. Please contact Technical Support for assistance with items outside the scope of this guide, including custom fiber components for optogenetics.
The most straightforward method for in vivo light stimulation of a specimen is to use a single fiber optic with a single LED light source. The single wavelength LED is powered by an LED driver, and then the illumination output is fiber-coupled into a patch cable, which connects to the implanted cannula. See the graphics and expandable compatibility tables below for the necessary patch cables and cannulae to create this setup. To choose the appropriate LED and driver, see below or the full web presentation.
Click on Each Component for More Information
Click to See Ø1.25 mm (LC) Ferrule Compatible Patch Cables, Cannulae, and Interconnects
Click to See Ø2.5 mm (FC) Ferrule Compatible Patch Cables, Cannulae, and Interconnects
The ability to accurately and simultaneously direct light to multiple locations within a specimen is desired for many types of optogenetics experiments. For example, bilateral stimulation techniques typically target neurons in two spatially separated regions in order to induce a desired behavior. In more complex experiments involving the simultaneous inhibition and stimulation of neurons, delivering light of two different monochromatic wavelengths within close proximity enables the user to perform these experiments without implanting multiple cannulae, which can increase stress on the specimen.
Bilateral stimulation can be achieved with several different configurations depending on the application requirements. The sections below illustrate examples of different configurations using Thorlabs' optogenetics products.
Thorlabs' RJ2 1x2 Rotary Joint Splitter is designed for optogenetics applications and is used to split light from a single input evenly between two outputs. The rotary joint interface allows connected patch cables to freely rotate, reducing the risk of fiber damage caused by a moving specimen. See the graphic and compatibility table below for the necessary cables and cannulae to create this setup. For LEDs and drivers, see below or the full web presentation.
Click to See Ø1.25 mm (LC) Ferrule Components Recommended for Use with RJ2 Rotary Joint Splitter
Click to See Ø2.5 mm (FC) Ferrule Components Recommended for Use with RJ2 Rotary Joint Splitter
If the intent is for one LED source to connect to two cannulae for simultaneous light modulation, then a bifurcated fiber bundle can be used to split the light from the LED into each respective cannula. For dual wavelength stimulation (mixing two wavelengths in a single cannula) or a more controlled split ratio between cannula, one can use a multimode coupler to connect one or two LEDs to the cannulae. If one cable end is left unused, the spare coupler cable end may be terminated by a light trap. See the graphic and compatibility table below for the necessary cables and cannulae to create this setup. For LEDs and drivers, see below or the full web presentation.
Click on Each Component Below for More Information
For bilateral stimulation applications where the two cannulas need to be placed in close proximity (within ~1 mm), Thorlabs offers dual-core patch cables and cannulae that are designed for this specific application. Each core is driven by a separate light source, enabling users to stimulate and/or supress nerve cells in the same region of the specimen. See the graphic and compatibility table below for the necessary cables and cannulae to create this setup. For LEDs and drivers, see below or the full web presentation.
Click on Each Component for More Information
|Part Selection Table (Click Links for Item Description Popup)|
|Common Fiber Properties|
|Core Diameter||200 µm|
|Wavelength Range||400 - 2200 nm|
|Ferrule Stylea||FC (Ø2.5 mm)|
|Dual-Core Patch Cable||FC/PC Input||BFY32FL1|
|Compatible Mating Sleeve/Interconnect||ADAF1
|Dual-Core Fiber Optic Cannulaec||Stainless Steel||CFM32L10
|LED Item #||Wavelengtha||Typical Opsin||Output Powerb||Color|
|M385F1c||385 nm||EBFP, moxBFP||10.7 mW||UV|
|M405F1c||405 nm||mmilCFP, hcriGFP||3.7 mW||UV|
|M430F1||430 nm||ChR2||7.5 mW||Violet|
|M455F3||455 nm||ChIEF, bPAC||24.5 mW||Royal Blue|
|M505F3||505 nm||ChRGR, Opto-α1AR, Opto-β2AR||11.7 mW||Cyan|
|M530F2||530 nm||C1V1, VChR1||9.6 mW||Green|
|M565F3||565 nm||Arch, VChR1-SFO||13.5 mW||Lime|
|M595F2||595 nm||ChR2-SFO, eNpHR3.0||11.5 mW||Amber|
|M625F2||625 nm||ReChR||17.5 mW||Red|
Click to Enlarge
Our fiber-coupled LEDs are ideal light sources for optogenetics applications. They feature a variety of wavelength choices and a convenient interconnection to optogenetics patch cables. Thorlabs offers fiber-coupled LEDs with nominal wavelengths ranging from 280 nm to 1050 nm. See the table to the right for the LEDs with the most popular wavelengths for optogenetics. A table of compatible LED drivers can be viewed by clicking below.
||400 - 2200 nm||200 µm ± 5 µm||700 µm||0.39||118 g||2.5 mm||Stainless Steel||Two FC/PC to Ferrule||CFM32 Dual-Core Cannulae||-50 to 60 °C|
|BFY32SL1||Two SMA905 to Ferrule|
These dual-core cannulae are designed to be used with the dual-core patch cables sold above. They are connected to patch cables using mating sleeves or the quick release interconnect.
|Image||Ferrule Type||Fiber Type||Fiber Core|
|Core Spacing||NA||Wavelength Range||Compatible Patch Cables|
|Ø2.5 mm x 10 mm, Stainless||FT200EMT||200 ± 5 µm||225 ± 5 µm||700 µm||0.39 ± 0.02||400 - 2200 nm||BFY32 Dual-Core Patch Cables|