NRT-2500 Polarization Controller

The NRT-2500 is a versatile Polarization Control Platform, offering multiple built-in polarization control functions for optical transponder, device and sub-system development and manufacturing.






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NRT-2500 Polarization Controller

NRT’s polarization control platform combines an integrated-optic Lithium Niobate (LiNbO3) waveguide polarization-controller device for super-fast polarization response driven by a customizable DSP/FPGA platform for functional flexibility. Together they enable NRT to provide a wide range of polarization operations in one product. There are currently five six polarization functions described below.

Polarization Functions

1. Paddles (Set Polarization)

This is perhaps the most common polarization control operation used in the lab. The NRT-2500 provides the electronic equivalent of 4 Lefevre fiber-optic paddles to align the pump to the probe or the signal to the local oscillator, maximize light through a polarization element, or polarization-demultiplex optical communication signals.

Each ‘electronic paddle’ is controlled through the user interface to set the polarization where you need it. Move the sliders or enter a values from 0 to 1000.

 GUI for Paddle Mode

GUI for Paddle Mode

2. Scrambler

The NRT State of Polarization (SOP) Scrambler provides full and uniform coverage of the Poincaré Sphere characterized by a stochastic Rayleigh distribution of SOP speeds. This mode is invaluable for testing the robustness of polarization tracking and locking schemes.

The NRT-2500’s Scrambler repeatably generates this well- known  stochastic  analytic  distribution  of  SOP  speeds.  No more guessing about the coverage of the Poincaré sphere or the distribution of SOP change rates. Just enter the desired Rayleigh distribution scrambling rate and you’re on your way.


Histogram of Scrambler Speed distribution Uniform Poincaré Sphere Coverage (insert)

3. Depolarizer

The most recent addition to the NRT-2500 polarization functions is the Depolarizer. As the name implies, the Depolarizer is a (single speed) ultrafast scrambler designed to reduce the degree of polarization of the measured signal. The Depolarizer is primarily used to remove PDL from power measurement and detector calibration.

depolarizer histogram

Mean SOP speed ~ 300krad/sec

depolarizer coverage

Uniform SOP coverage

4. Spinner

New  generation  coherent  PM-QPSK  transceivers,  for  40G, 100G  and above communications systems, require verification testing to assure the operate reliably even when the SOP changes extremely rapidly. The Spinner Mode simulates a 1⁄2-waveplate, rotating the SOP up to 75 KHz (>470,000 rad/sec for linearly polarized light), controllably, repeatably endlessly to stress these transceivers.

Spinner on S1-S2 Poincare

Perfect Rotating-Half-Waveplate

spinner histogram

Spinner Histogram

5. Randomizer

The NRT-2500 Polarization Randomizer mode randomly ‘jumps’ the output SOP about the Poincaré sphere every (user-input) time interval, or when triggered by externally. The trigger mode is useful to simulate the SOP temporal response to lighting strikes on coherent DSP receivers or to change the SOP at every pass through a fiber loop testbed.

Example of ultrafast Randomizer SOP event.

randomizer on sphere

Sample Randomizer jump

∆SOP through a polarizer

∆SOP through a polarizer


6. Tracker

Fast Robust and Endless Polarization NRT’s unique tracking algorithm enables virtually perfect SOP tracking with no dropouts or ‘glitches’ for your new applications and  prototypes.  The NRT-2500’s open architecture allows you to optimize the performance for your specific application:

  1. Create  a  unique  error  signal  from  four A/D  converter inputs,
  2. Optimize algorithm parameters with Tracker’s ‘Optimizer’ program.

New Ridge has leveraged many years of experience in the Tracker. And has packaged it all together for you. The Tracker’s technology is so robust, it has been incorporated in multiple systems and qualified for network deployment at a number of carriers worldwide.

Simple Tracker demo set-up

Simple Tracker demo set-up


Tracker on the Poincaré Sphere

The tracker function is also offered in OEM daughter-card formats for your system application. See the NRT-250 page.

Sample Applications

  1. Optical Polarization Demultiplexing
  2. PMD tolerance testing of transponders
  3. Optical polarization demuxing
  4. Testing electronic pol-demux
  5. Optical PMD compensation
  6. Coherent detection
  7. Detector calibration
  8. Ultrafast ∆SOP/∆t event generation
  9. Power combining

Additional information

Dimensions 10.26 × 25.7 × 31.3 cm
Insertion Loss < 3 dB
PDL < 0.3 dB
Optical return Loss > 50 dB
Optical Power Handling < 20 dBm
Operating Wavelength 1.55 microns (C- and L-bands)
Optical Connectors FC/UPC, FC/APC, SC
Scrambler mode SOP Speed up to 3,400 rad/sec for rmode ≡ b0.5 of a Rayleigh distribution2
Spinner mode rate 940,000 rad/sec on great circle orientation for 75 kHz drive
Randomizer mode SOP speed up to 2,250,000 rad/sec3
Depolarizer mode SOP speed over 3,000,000 rad/sec4
Tracker mode update time ~20 microseconds5
Power Supply 12 VDC from 100-240 VAC, 50 – 60 Hz, AC-DC converter
Communication Interfaces RS-2326
Dimensions H=4.04” (102.6 mm), W=10.12” (257 mm), D=12.32” (313mm)
1. Subject to change at any time by New Ridge Technologies, LLC.

2. For a Rayleigh distribution: rmode is the statistical mode of the distribution, ⟨r⟩ is the mean SOP change, and 99.9% of all SOP changes occur before rmax = 3⟨r⟩ ~ 3.76rmode

3. Calculated assuming π radians on Poincaré sphere in 1.4 µs.

4. Non-stochastic dSOP/dt distribution from 0 to >3 Mrad/sec completely covering Poincaré sphere.

5. This speed is the closed loop feedback/update algorithm loop time based on reading A/DCs and DSP speed and updating polarization controller voltages. The feedback signal detector response time and customization of the algorithm may slow system response.

6. RS-232-to-USB dongle provided with each NRT-2500.