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10 GHz Lithium Niobate Modulators


  • 10 GHz Intensity Modulators, X- and Z-Cut LiNbO3
  • 10 GHz Phase Modulators, Z-Cut LiNbO3

LN53S-FC

Phase Modulator

LN81S-FC

Zero-Chirp Intensity Modulator

LN82S-FC

0.7 Fixed-Chirp Intensity Modulator

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10 GHz Intensity Modulator, Fixed Chirp

Parameter Value
Operating Rangea 1525 - 1605 nm
Optical Insertion Loss 4.0 dB (Typical)
Electro-Optic Bandwidth (-3 dB) 10 GHz (Min)
  • The modulator is designed for use at the specified wavelengths. Using the modulator at other wavelengths may cause an increase in the optical loss that is not covered under warranty. In some cases, this loss can be temporary; for instance, the increase in loss caused by shorter wavelengths can usually be reversed by heating the modulator to 80 °C for an hour.

Features

  • C- and L-Band Operation Range
  • Low Optical Insertion Loss: 4.0 dB (Typical)
  • Titanium Indiffused Z-Cut Lithium Niobate
  • Low Drive Voltage
  • Long-Term Bias Stability
  • Telcordia GR-468 Compliant
  • Integrated Photodetector

The LN82S-FC is a 10 GHz LiNbO3 intensity modulator with a fixed chirp of 0.7 and an integrated photodiode. The modulator features a PM input fiber pigtail and an SM output fiber pigtail that are terminated with FC/UPC (ultra physical contact) connectors. The PM fiber is keyed to the slow-axis, which is also aligned to the extraordinary mode. The integrated photodetector can be used for optical power monitoring and modulator bias control, which eliminates the need for an external fiber tap. RF input into the modulator is supplied via a GPO® connector.

These modulators are fabricated from Titanium Indiffused Z-Cut LiNbO3, which creates an inequality in the push-pull phase shift between the two arms of the Mach-Zehnder interferometer. This results in a phase/frequency shift (chirp) in the output in addition to the intensity modulation. These fixed chirp modulators down-chirp the pulse, which can be useful when the optical fiber in the network has a positive dispersion coefficient. The down-chirped pulse traveling through an optical fiber with a positive dispersion coefficient will be compressed until a minimum is reached. Beyond that point the dispersion term will dominate. Since chirping the pulse increases the spectral width of the pulse, the chirped pulse will eventually be broader than an unchirped pulse traveling through the same optical fiber. This fixed chirp intensity modulator is ideal for applications requiring improved power penalty (less than two dB for +1600 ps/nm) performance over zero-chirp devices. For telecommunications applications, the LN82S-FC can be easily integrated into 300-pin MSA-compatible transponders.

These modulators have an SMP-male connector for the GPO input drive that can mate with an SMP-female connector, which can then be adapted to an SMA connector. To do this, we recommend using our SMA-to-SMP Microwave Adapter Cables or a GPO to K™ adapter. The GPO to K adapter is available for purchase upon request*. Other third party SMP adapters are available from various electronics component suppliers, but the fit may vary and compatibility is not guaranteed. For more information on custom configurations (i.e., fiber type, connectorization, etc.) and quotes, please contact Technical Support

*Please be advised that because of the compact modulator package, the modulator may not sit flat on a table after attaching a GPO to K adapter, but will sit flat when using the SMP to SMA cable. These specific adapters have been verified to fit the GPO or SMP connector on the package, and have been used for testing purposes. 

GPO® is a registered trademark of Corning Gilbert. K™ is a trademark of Anritsu.

Parameter Min Typical Max
Optical
Operating Wavelengtha 1525 nm - 1605 nm
Optical Insertion Loss - 4.0 dB 5.0 dB
Optical Return Loss 40 dB - -
Optical Extinction Ratio (@ DC) 20 dB - -
Optical Input Power - - 100 mW
Electrical
E/O Bandwidth (-3 dB) 10 GHz 14 GHz -
Operating Frequency Range DC to 15 GHz (Min)
RF Vπ (@ 1 GHz) - 5.2 V 6.5 V
DC Bias Vπ (@ 1 kHz)b - 2.7 V 3.0 V
S11 (DC to 10 GHz) - -12 dB -10 dB
RF Port Input Power - - 24 dBm
Photodetector
Reverse Bias Voltage -5.5 V - -3.0 V
Responsivity 0.1 mA/mW - 0.5 mA/mW
Output Optical Power Monitoring Range
-5 dBm - 10 dBm
Mechanical
Crystal Orientation Z-Cut
RF Connection Male SMP (GPO® Compatible)
Fiber Type Input: PANDA Polarization Maintaining
Output: SMF-28® Single Mode
Fiber Lead Length 1.5 m (Typ.)
Environmental
Operating Temperature 0 °C - 70 °C
Storage Temperature -40 °C - 85 °C
  • The modulator is designed for use at the specified wavelengths. Using the modulator at other wavelengths may cause an increase in the optical loss that is not covered under warranty. In some cases, this loss can be temporary; for instance, the increase in loss caused by shorter wavelengths can usually be reversed by heating the modulator to 80 °C for an hour.
  • The LN82S-FC includes a bias circuit that couples the DC bias onto the RF drive electrode. Depending on the application, an external DC block may be needed at the RF input.
Pin Label (Number) Description
C (1) Photodetector Cathode
A (2) Photodetector Anode
B (3) Modulator DC Bias
G (4) Modulator Bias Ground

RF Modulation Input: SMP RF Connector


Posted Comments:
hnguyen43  (posted 2018-05-07 11:00:34.96)
Can this modulator work for the wavelength range between 1100-1180nm? If not, can you customize an intensity modulator for that wavelength range?
YLohia  (posted 2018-05-09 10:29:58.0)
Thank you for contacting Thorlabs. At 1100-1180 nm, while these modulators can technically be used, the waveguides will definitely not be single mode; they will be multi-mode due the cut-off wavelength being specified at 1290-1450 nm. The insertion loss, modulation efficiency (Vpi), extinction ratio, etc. will all change considerably from the values that we specify at 1550nm. Unfortunately, we are unable to offer a custom GHz modulators based on wavelength range at the moment.
akg  (posted 2018-01-31 22:22:19.57)
Hello, I am looking for a setup which looks like: SFL1550P ---> LN82S-FC (or LN81S-FC) ---> LN53S-FC Please suggest if there will be issues in above interconnections. Specifically input of LN53S-FC is polarization maintaining while the output of LN82S-FC is not. Please comment on this and contact me as I wish to proceed quickly. Atul
tfrisch  (posted 2018-02-06 10:04:01.0)
Hello Atul, thank you for contacting Thorlabs. You will need to be sure that the SM fiber of LN82S-FC launches the light aligned to the PM ax is of LN53S-FC. This could be achieved with a fiber polarization controller. Alternatively, we are able to offer LN82S-FC with a PM fiber on both the input and output. I will reach out to you directly to discuss which of these options is more suitable for your application.
benjamin.haylock2  (posted 2017-05-04 15:46:46.647)
Is it safe to solder the DC pins?
nbayconich  (posted 2017-05-22 09:43:08.0)
Thank you for contacting Thorlabs. The pins on our Lithium Niobate Intensity Modulators are intended to be soldered. A Techsupport representative will contact you directly.
nasertrus  (posted 2017-03-21 08:43:05.833)
Hello! How to manage optical modulator LN82S-FC? It have SMP connector and 4 pin? What I must do to modulate input signal? Sorry, but I can't find this information in the Manual.
tfrisch  (posted 2017-03-30 05:10:52.0)
Hello, thank you for contacting Thorlabs. I see you have already been in contact with a member of our Technical Support Team about the pin diagrams and operation techniques.
mlaroton  (posted 2017-03-15 08:24:51.667)
Hi, do your 10 GHz intensity modulators (LN82S-FC, or LN81S-FC) include a built-in polarizer? We plan to use them in a double pass setup with a reflection upon a faraday mirror so it is crucial that both polarizations can circulate through the device. Thank you very much, Miguel
tfrisch  (posted 2017-03-15 09:38:00.0)
Hello, thank you for contacting Thorlabs. While these modulators do not have internal polarizers, they are sensitive to polarization. Furthermore, they are not fully bidirection, and performance would be very limited in the reverse direction. I will reach out to you directly with details.
saranha1001  (posted 2016-07-12 10:44:28.417)
What is the polarization dependent loss of this product? I couldn't find it in the spec.
user  (posted 2016-06-20 13:02:19.567)
Hello, It seems like my int. modulator react only for increasing slope of modulating RF signal (3,5-4,5V, 0-15Mhz, square signal). (Modulated signal is similar to triangles). I would like to ask, is it too low rf signal frequency, or maybe this modulator feature is to react only for that slope? But if yes, then how to demodulate logical 0 ?
besembeson  (posted 2016-06-22 09:12:51.0)
Response from Bweh at Thorlabs USA: Please contact me at techsupport@thorlabs.com to further discuss your application.
yue.s  (posted 2016-05-19 06:06:14.71)
What is the max input optical power for the intensity modulator LN82S-FC? moreover is the RF and DC voltage mentioned in the spec are the average value or the peak value?
besembeson  (posted 2016-05-19 04:11:36.0)
Response from Bweh at Thorlabs USA: We recommend keeping the input power to under 100mW. That is the RMS voltage.
Thorlabs  (posted 2010-10-19 19:23:08.0)
Response from Javier at Thorlabs to jikim: There are some slight differences between the x-cut (LN56/LN81) and z-cut (LN63/LN82) 10G intensity modulators, but the variation in the Vpi of the RF port is typically in the following range: DC to 1 GHz = 5V, 3GHz = 5.5V, 10 GHz = 7V. Note, the Vpi @ DC quoted in the specification sheet is for the DC bias port - not the RF port. The Vpi of the RF port is tested and specified with a 10Gb/s pseudo-random bit sequency (PRBS) which has a frequency spectrum that is roughly equivalent to a fixed frequency in the 3-4 GHz range, that is why the Vpi @ 3 GHz above is indicated as being equivalent to the Vpi for the 10 Gb/s PRBS.
jikim  (posted 2010-10-19 11:00:14.0)
According to the specification, the Vp is mentioned to be in the range of 3 to 8 V. Could you show the frequency dependence of such a voltage on the frequency (from 0 to 10 GHz)?
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
LN82S-FC Support Documentation
LN82S-FCFixed-Chirp, 10 GHz Intensity Mod., Integrated PD and Replaceable SMP Connector, FC/PC
$2,461.70
Today

10 GHz Intensity Modulator, Zero Chirp

Parameter Value
Operating Rangea 1525 - 1605 nm
Optical Insertion Loss 4.0 dB (Typical)
Electro-Optic Bandwidth (-3 dB) 10 GHz (Min)
  • The modulator is designed for use at the specified wavelengths. Using the modulator at other wavelengths may cause an increase in the optical loss that is not covered under warranty. In some cases, this loss can be temporary; for instance, the increase in loss caused by shorter wavelengths can usually be reversed by heating the modulator to 80 °C for an hour.

Features

  • C- and L-Band Operation Range
  • Low Optical Insertion Loss: 4.0 dB (Typical)
  • Titanium Indiffused X-Cut Lithium Niobate
  • Low Drive Voltage
  • Long-Term Bias Stability
  • Telcordia GR-468 Compliant
  • Integrated Photodetector

The LN81S-FC is a 10 GHz LiNbO3 intensity modulator with zero chip and an integrated photodiode. It can provide intensity modulation from DC to >15 GHz for applications such as RF photonics, telecommunications, and sensing. The modulator features a PM input fiber pigtail and an SM output fiber pigtail that are terminated with FC/UPC (ultra physical contact) connectors. The PM fiber is keyed to the slow-axis, which is also aligned to the extraordinary mode. The integrated photodetector can be used for optical power monitoring and modulator bias control, which eliminates the need for an external fiber tap. RF input into the modulator is supplied via a GPO® connector.

These modulators are fabricated from X-Cut Titanium Indiffused LiNbO3, which allows for both arms of the Mach-Zehnder interferometer to be symmetrically modulated. This symmetry ensures that the modulated output of the intensity modulator is not also shifted in phase/frequency (chirped). Chirp is an important factor in high-data-rate, long-distance telecommunication systems. The optimum value (typically zero or ~0.6) depends signficantly upon the overall system architecture. Zero-chirp intensity modulators, in particular, are ideal for use in metro and long-haul DWDM applications requiring less than a 2 dB power penalty for ±1200 ps/nm dispersion. For telecommunications applications, the LN81S-FC can be easily integrated into 300-pin MSA-compatible transponders.

These modulators have an SMP-male connector for the GPO input drive that can mate with an SMP-female connector, which can then be adapted to an SMA connector. To do this, we recommend using our SMA-to-SMP Microwave Adapter Cables or a GPO to K™ adapter. The GPO to K adapter is available for purchase upon request*. Other third party SMP adapters are available from various electronics component suppliers, but the fit may vary and compatibility is not guaranteed. For more information on custom configurations (i.e., fiber type, connectorization, etc.) and quotes, please contact Technical Support

*Please be advised that because of the compact modulator package, the modulator may not sit flat on a table after attaching a GPO to K adapter, but will sit flat when using the SMP to SMA cable. These specific adapters have been verified to fit the GPO or SMP connector on the package, and have been used for testing purposes. 

GPO® is a registered trademark of Corning Gilbert. K™ is a trademark of Anritsu.

Parameter Min Typical Max
Optical
Operating Wavelengtha 1525 nm - 1605 nm
Optical Insertion Loss - 4.0 dB 5.0 dB
Optical Return Loss 40 dB - -
Optical Extinction Ratio (@ DC) 20 dB - -
Optical Input Power - - 100 mW
Electrical
E/O Bandwidth (-3 dB) 10 GHz 14 GHz -
Operating Frequency Range DC to 15 GHz (Min)
RF Vπ (@ 1 GHz) - 5.6 V 6.5 V
DC Bias Vπ (@ 1 kHz) - 6.5 V 10.0 V
S11 (DC to 10 GHz) - -12 dB -10 dB
RF Port Input Power - - 24 dBm
Photodetector
Reverse Bias Voltage -5.5 V - -3.0 V
Responsivity 0.1 mA/mW - 0.5 mA/mW
Output Optical Power Monitoring Range
-5 dBm - 10 dBm
Mechanical
Crystal Orientation X-Cut
RF Connection Male SMP (GPO® Compatible)
Fiber Type Input: PANDA Polarization Maintaining
Output: SMF-28® Single Mode
Fiber Lead Length 1.5 m (Typ.)
Environmental
Operating Temperature 0 °C - 70 °C
Storage Temperature -40 °C - 85 °C
  • The modulator is designed for use at the specified wavelengths. Using the modulator at other wavelengths may cause an increase in the optical loss that is not covered under warranty. In some cases, this loss can be temporary; for instance, the increase in loss caused by shorter wavelengths can usually be reversed by heating the modulator to 80 °C for an hour.
Pin Label (Number) Description
C (1) Photodetector Cathode
A (2) Photodetector Anode
B (3) Modulator DC Bias
G (4) Modulator Bias Ground

RF Modulation Input: SMP RF Connector


Posted Comments:
jason.a.willis99  (posted 2018-01-04 14:32:16.553)
Could you please send me the application note for this product?
tfrisch  (posted 2018-01-04 03:06:47.0)
Hello, thank you for contacting Thorlabs. I will send you the application note as well as a link to our Lab Fact presentation which has some information on driving modulators which may be relevant to these amplitude modulators as well as the phase modulators used in the experiment.
tbarrett  (posted 2014-01-08 13:37:44.233)
Does this product have a users manual?
jlow  (posted 2014-01-09 04:08:34.0)
Response from Jeremy at Thorlabs: The LiNbO3 modulators come with a characterization sheet with a drawing showing the pin-outs of the modulators. There's no user manual but I will send to you an application note for your reference.
tcohen  (posted 2012-12-28 13:06:00.0)
Response from Tim at Thorlabs: This is a Mg doped LiNbO3 crystal. This material will form color centers when exposed to light at 780nm, causing higher loss. This is temporary as charge carriers become displaced and trapped in defects, forming dipoles within the crystal, and may be removed by heating. For modulation, there are suitable RF amplifiers available from companies such as SHF, Triquint, Oki, Inphi, Centellax, Picosecond, etc. We will contact you directly to discuss your application in more detail.
gnishi  (posted 2012-12-17 00:46:58.797)
Dear Sir: I have a question on the modulator. (1) Can it be used for the modulation with 780nm wavelength? If so, is there any problem with such wavelength region or anything to concern for the opearation? (2) Do you have a product for driving this modulator? Thank you for advance.
bdada  (posted 2011-11-01 12:37:00.0)
Response from Buki at Thorlabs: Thank you for your feedback. Our production team will review your suggestion. Please contact TechSupport@thorlabs.com if you would like to discuss your application further.
user  (posted 2011-10-31 12:57:03.0)
Please look at adding a SMA to SMP connector as you sell SMA cables but not SMP.
jjurado  (posted 2011-06-15 09:54:00.0)
Response from Javier at Thorlabs to jikim: Thank you very much for contacting us. At the moment, we do not have the capability to offer such a product. Free-space modulators do not have the capability to achieve 40 dB extinction ratio performance, and producing a fiber coupled LN-type modulator with free-space output would require a significant amount of development. Alternatively, we could supply a short length of PM fiber at the output pigtail, which could be then fitted with a collimator. However, we cannot commit to a 40 dB PER specification. I will contact you directly to get more details about your application.
jikim  (posted 2011-06-14 15:17:06.0)
Could you provide a customized phase modulator with a PM input (FC/APC) and a free space collimated output to obtain the linear polarization output with extinction ratio more than 40 dB and without ellipticity? In the fiber output there exists thermal effects.
jikim  (posted 2011-03-08 16:13:26.0)
Is a zero chirp intensity modulator (LN56S-FC) with a PM fiber in the output available? I would appreciate if you could send me a quotation for it.
user  (posted 2011-02-13 22:03:34.0)
Thorlabs  (posted 2010-10-07 15:08:16.0)
Response from Javier at Thorlabs to Andres: I will contact you directly to discuss your application. We have to first consider your lasers wavelength and power output, among other parameters.
andres.aragoneses  (posted 2010-10-07 11:57:04.0)
Dear sir/madam I need an optic amplifier that multiplies the intensity of one laser an integer number of times (2, 3 or 4). Which is the product I need? thank you Aragoneses
Adam  (posted 2010-05-06 16:24:13.0)
A response from Adam at Thorlabs: We are working on getting these drawings on the web. In the meantime, if you need the drawings please email techsupport@THorlabs.com and we will provide with the necessary documentation.
user  (posted 2010-05-05 21:38:35.0)
can you please provide mechanical drawings for those products?
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
LN81S-FC Support Documentation
LN81S-FCZero-Chirp, 10 GHz Intensity Mod., Integrated PD and Replaceable SMP Connector, FC/PC
$2,461.70
Today

10 GHz Phase Modulators

Parameter Value
Operating Wavelength Rangea 1525 - 1605 nm
Optical Insertion Loss
3.0 dB (Typical)
Electro-Optic Bandwidth (-3 dB) 10 GHz (Typ.)
  • The modulator is designed for use at the specified wavelengths. Using the modulator at other wavelengths may cause an increase in the optical loss that is not covered under warranty. In some cases, this loss can be temporary; for instance, the increase in loss caused by shorter wavelengths can usually be reversed by heating the modulator to 80 °C for an hour.

Features

  • C- and L-Band Operation Range
  • Low Optical Insertion Loss: 3.0 dB (Typical)
  • Titanium Indiffused Z-Cut Lithium Niobate
  • Low Drive Voltage
  • Telcordia GR-468 Compliant
  • Optional Integrated Output Polarizer

These Titanium Indiffused Z-Cut LiNbO3 Phase Modulators are available with (LN63S-FC) or without (LN53S-FC) an integrated polarizer. Phase modulators provide chirp control in high-speed data communications. They are also ideal for coherent communications, sensing, all-optical frequency-shifting, and data encryption applications.

These Z-Cut LiNbO3 phase modulators are 10 GHz devices with a PM input fiber pigtail and a SM output fiber pigtail. Both are terminated with FC/PC connectors. The LN65S-FC has an integrated optical polarizer positioned before the output port of the device. The integrated polarizer is not included with the LN53S-FC. With no polarizer, the device is capable of supporting both optical modes, ordinary and extraordinary. Each mode will have a different modulation efficiency; the modulation efficiency of the extraordinary mode will be approximately a factor of three greater than the ordinary mode. For those interested in supporting only the extraordinary mode, the internal polarizer would be desirable.

These modulators have an SMP-male connector for the GPO® input drive that can mate with an SMP-female connector, which can then be adapted to an SMA connector. To do this, we recommend using our SMA-to-SMP Microwave Adapter Cables or a GPO to K™ adapter. The GPO to K adapter is available for purchase upon request*. Other third party SMP adapters are available from various electronics component suppliers, but the fit may vary and compatibility is not guaranteed. For more information on custom configurations (i.e., fiber type, connectorization, etc.) and quotes, please contact Technical Support

*Please be advised that because of the compact modulator package, the modulator may not sit flat on a table after attaching a GPO to K adapter, but will sit flat when using the SMP to SMA cable. These specific adapters have been verified to fit the GPO or SMP connector on the package, and have been used for testing purposes. 

GPO® is a registered trademark of Corning Gilbert. K™ is a trademark of Anritsu.

Parameter Min Typical Max
Optical
Operating Wavelengtha 1525 nm - 1605 nm
Optical Insertion Loss - 3.0 dB 4.5 dB
Optical Return Loss 40 dB - -
Optical Input Power - - 100 mW
Electrical
S11 (DC to 10 GHz) - -12 dB -10 dB
E/O Bandwidth (-3 dB) - 10 GHz -
Operating Frequency Range DC to 15 GHz (Typ.)
RF Vπ (@ 10 GHz) - 7.5 V 9.5 V
RF Port Input Power - - 24 dBm
Mechanical
Crystal Orientation Z-Cut
RF Connection Male SMP (GPO® Compatible)
Fiber Type Input: PANDA Polarization Maintaining
Output: SMF-28® Single Mode
Fiber Lead Length 1.5 m (Typ.)
Environmental
Operating Temperature 0 °C - 70 °C
Storage Temperature -40 °C - 85 °C
  • The modulator is designed for use at the specified wavelengths. Using the modulator at other wavelengths may cause an increase in the optical loss that is not covered under warranty. In some cases, this loss can be temporary; for instance, the increase in loss caused by shorter wavelengths can usually be reversed by heating the modulator to 80 °C for an hour.
Pin Label (Number) Description
C (1) Not Connected
A (2) Not Connected
B (3) Not Connected
G (4) Not Connected

RF Modulation Input: SMP RF Connector

Driving an Electro-Optic Phase Modulator with the Amplified Output of a Function Generator

Vpi
Click to Enlarge

Figure 1: Experimental Setup Used to Evaluate Whether a Basic RF Source Built Around a Function Generator Could be Sufficient to Drive a Fiber-Coupled EO Phase Modulator

Thorlabs offers a selection of fiber-coupled electro-optic (EO) modulators, which are ideal for modulating light from fiber-coupled laser sources. Applications frequently require EO modulators to be driven at rates of 1 GHz or higher, which places significant demands on the driving radio frequency (RF) voltage source. We investigated whether it would be possible to use a basic setup built around a function generator to drive a fiber-coupled EO phase modulator. The experimental setup we designed and implemented to test this possibility included instrumentation to record the spectrum of the modulated optical signal. By analyzing the modulated optical spectrum, we confirmed this basic RF source is a viable option for driving a fiber-coupled EO phase modulator. Our approach and results are documented in this Lab Fact.

Experimental Design and Setup

The design of the RF voltage source portion of the setup required first determining the power the RF source should supply to drive the fiber-coupled EO phase modulator. The power requirements were calculated after we made an estimate of the driving voltage needed to achieve the modulation depth desired for this application. Details describing our process for selecting a modulation depth, the relationship between modulation depth and driving voltage, and the calculations we used to estimate the power required from the RF voltage source are included in the Lab Facts document. From our investigations, we determined the power from the function generator alone would not be sufficient for our application. Our solution was to insert a low noise amplifier between the function generator and EO modulator. We also included an electrical low pass filter before the modulator to remove signal distortion that appeared to originate with the function generator. We drove the EO phase modulator with a sinusoidal RF voltage, which imparted a sinusoidal phase modulation on the 1550 nm CW laser signal.

A scanning Fabry-Perot interferometer, whose output was sent to an oscilloscope, was placed after the EO phase modulator and used to measure and monitor the spectrum of the modulated optical signal. It was necessary to use the Fabry-Perot interferometer for this purpose as it has the ability to resolve the very fine spectral features of the phase-modulated optical spectra: at a wavelength of 1550 nm, a frequency difference of 1 GHz is equivalent to a wavelength difference of 0.8 pm. The measured spectra were recorded as functions of scan time. In the Lab Facts document, we describe a straight-forward method to convert from units of Fabry-Perot scan time to units of relative optical frequency. For this work, we estimate Δf = (1.17 GHz/ms)Δt.

Experimental Results

As is described in the Lab Facts document, theory predicts the spectra of our phase modulated optical signals would include sets of symmetric sidebands arranged around the laser carrier peak at frequency fo. The sidebands are displaced from the laser carrier peak frequency at integer multiples of the modulation frequency fm (fo ± Nfm with N = 1, 2, ...). The relative heights of the sidebands are a function of the modulation depth, which is in turn a function of the peak-to-peak value of the RF driving voltage. Given the modulation depth, the relative amplitudes of the laser carrier peak and modulation sidebands can be calculated. This makes it possible to tailor the power distribution across the various peaks to meet an application's needs. We used the predictive power of this model to confirm our RF source was adequately driving the EO modulator.

The spectra shown in Figures 2 and 4 are representative of the modulation spectra we measured. The theoretical curves in Figure 3 are a function of modulation depth and plot the expected relative powers of the laser carrier peak (solid red curve), first order sidebands (dotted blue curve), second order sidebands (dotted green curve), and third order sidebands (dotted violet curve). The black arrow points to the modulation depth corresponding to the spectrum in Figure 2, and the gray arrow points to the modulation depth corresponding to the spectrum in Figure 4. From our results, we determined our measured and applied modulation frequencies agreed, and we confirmed the spectral power distributions in our optical spectra were consistent with the peak-to-peak driving voltage of the RF source. We conclude that the good agreement between the expected and recorded results validates the use of a basic RF source built around a function generator as a driver for fiber-coupled EO phase modulators. 

EO Phase Modulator Spectrum for Vpp 3.63
Click to Enlarge

Figure 4: EO Phase Modulator Spectrum When Vpp = 3.63 V
The carrier frequency is fo; the modulation frequency is fm = 1 GHz. The X-axis reports the scanning time of the Fabry-Perot interferometer and can be directly related to the signal's relative frequency spectrum.
EO Phase Modulator Sideband Relative Power for 0.44 Modulation Depth
Click to Enlarge

Figure 3: Curves Relating the Power in the Carrier and Several Sideband Peaks as A Function of Modulatrion Depth
The 0.44 modulation depth indicated by the black arrow corresponds to Figure 2, and the 0.56 modulation depth indicated by the gray arrow corresponds to Figure 4.
EO Phase Modulator Spectrum for Vpp 2.85
Click to Enlarge

Figure 2: EO Phase Modulator Spectrum When Vpp = 2.85 V
The carrier frequency is fo; the modulation frequency is fm = 1 GHz. The X-axis reports the scanning time of the Fabry-Perot interferometer and can be directly related to the signal's relative frequency spectrum.


Posted Comments:
gregory.gaeumann  (posted 2018-08-31 11:52:53.037)
Hello, I would like to use your 10 GHz Phase modulator to generate large phase modulations (for serrodyne frequency shifting). Unfortunately, the maximal RF input power is limited to 24 dBm, which is quite low. Is this limit really critical or does it only lead to a slow warm-up of the device? In case it is critical, can you tell me the limiting factor? Thank you.
llamb  (posted 2018-09-07 11:21:10.0)
Thank you for contacting Thorlabs. We have only qualified these devices up to 24 dBm for the RF input power and for lifetime testing. The primary limiting factor is the termination circuit that utilizes thin film resistors. These resistors should be able to handle higher power levels if the device is properly heat sunk. I will reach out to you directly to discuss your application and some limitations further.
arjan.meskers  (posted 2017-07-21 15:50:31.39)
The description states "PM input fiber pigtail and a SM output fiber pigtail." PM fibers are by definition single mode (i.e. SM), however SM fibers are not by definition polarization maintaining. It is not clear to me if the output fiber is also polarization maintaining, this also holds for the product '10 GHz Intensity Modulator, Zero Chirp'. Could you clarify the type of output fiber?
tfrisch  (posted 2017-07-26 01:11:34.0)
Hello, thank you for contacting Thorlabs. The input fiber is polarization maintaining as the modulation will only occur for one linear input state. The output will be modulated, but since a single mode (and not PM) fiber is used, the polarization of the modulated signal can vary with stress and bends in the fiber. We can offer versions that have PM fibers on both sides as a custom if you need. I will reach out to you directly as well.
yingwah.wu.civ  (posted 2016-09-27 18:14:56.25)
Can LN65S-FC be used for transceiver pair for delay line purpose? Thanks,
jlow  (posted 2016-10-05 02:06:00.0)
Response from Jeremy at Thorlabs: I will contact you directly about your application.
user  (posted 2016-06-20 15:38:57.803)
Hello, What is the phase transition in this modulator? Is it standard 2 state 180 deg. or it's controlled by RF signal bias?
besembeson  (posted 2016-06-22 09:23:40.0)
Response from Bweh at Thorlabs USA: No it is not a two state modulator. The phase is controlled by the RF signal input.
jjurado  (posted 2011-02-07 10:26:00.0)
Response from Javier at Thorlabs to jikim: Thank you very much for submitting your inquiry. The LN53S does not rotate polarization. However, it functions as a variable waveplate, just like a Soleil-Babinet Compensator, when a voltage is applied to the modulator. The voltage changes the relative retardance between two orthogonal polarization modes. No intensity modulation would be observed if the input polarization is perfectly linear *and* if the linear polarization is launched on-axis to the PM input fiber. It is possible that the input polarization is not linear and/or not launched on axis to the modulator. Small misalignments between the PM fiber and LN crystal will create a small intensity modulated signal when passed through a linear analyzer. Also, use of single mode fiber at the output will allow the amplitude of the intensity modulated signal you observed to vary; just gently press on the fiber. The LN65S modulator, with an internal polarizer, will greatly suppress the undesired intensity modulation. If you need to retain the state of polarization at the output of the modulator, PM output fiber should be used. Also, this modulator can be supplied with FC/APC connectors.
jikim  (posted 2011-02-04 17:31:35.0)
I have a question on the output polarization of the phase modulator. A simple experiment has been performed. A single mode laser beam with linear polarization passes through a LN53S-FC modulator to which a sinusoidal signal at few tens of MHz is applied. The output of the modulator passes through a linear polarizer, i.e. a polarization analyzer. A photo diode (PD) observes the intensity of the transmitted beam through the polarizer. Then I could observe the same sinusoidal signal at the PD indicating that the output polarization of the modulator is varied with respect to the phase modulation. Such polarization variation of the output is absolutely not desirable in my application. When a PM fiber is used in the output port of the phase modulator instead of a SMF, is there any polarization change depending on the phase modulation? Or is there any suggestion from you to escape such a polarization change?
jjurado  (posted 2011-02-02 11:54:00.0)
Response from Javier at Thorlabs to jikim: Thank you very much for submitting your inquiry. We can certainly provide an LN65S-FC modulators with PM input and output fiber pigtails. I will contact you directly with pricing and lead time information.
jikim  (posted 2011-02-02 16:14:34.0)
Could you provide a LN65S-FC with PM fibers in both input and output ports?
Thorlabs  (posted 2010-10-11 17:47:13.0)
Response from Javier at Thorlabs to jikim: We can certainly quote a special FC/APC version of the LN53S-FC. I will contact you directly with more information.
jikim  (posted 2010-10-11 13:02:11.0)
Is it possible to make FC/APC instead of FC/PC connector of this phase modulator (LN53S-SC)?
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LN53S-FC Support Documentation
LN53S-FC10 GHz Phase Modulator without Polarizer, FC/PC Connectors
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LN65S-FC Support Documentation
LN65S-FC10 GHz Phase Modulator with Polarizer, FC/PC Connectors
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