The Keysight N7786C is a high-speed lithium-niobate based polarization controller with built-in polarimeter for monitoring and feedback to set and stabilize sequences of chosen output polarization states.
- Comprehensive polarization stabilization/control
- Fast switching capability
- Enables single-sweep spectral PDL measurements with photonic application software suite
- 1240 nm to 1650 nm operating wavelength range
- Robust, no moving optical part
This unit can operate in several modes:
- As a polarization stabilizer, it provides a stable output state of polarization (SOP) even with fluctuations and drifts of the input SOP. The stabilized output signal is guided in a standard single-mode fiber (SMF). The output SOP can be defined in the following ways:
- When the set-and-forget switch in the user interface is activated, the current SOP is stored and maintained, even if polarization changes occur on the instrument input.
- Defined Stokes: the target output SOP can be defined by the user using the Stokes parameters, which are then set using the polarization analyzer feedback,
- Defined sequence: the device switches the SOP of the output signal in a chosen pattern with a cycling speed of up to 100 kSOPs/s. - As an SOP switch, the N7786C cycles through a sequence of SOPs at a chosen rate up to more than 40 kHz. The internal settings for the SOP sequence are first determined with the stabilizer function for rapid direct switching. SOP switching occurs within a few microseconds. An electrical trigger input can be used to synchronize the scrambler with external events.
- As a traditional scrambler, the N7786C varies the output SOP in a random way. Full coverage of the Poincaré Sphere can be achieved within a few milliseconds.
- As a polarization analyzer, the instrument provides truly high-speed capabilities: Up to 1 M samples can be taken with a sample rate of up to 1 M samples per second.
- As fast-switching polarization controller for single-sweep wavelength dependent PDL measurements in combination with the photonics application software suite (PAS).
The instrument comes in a compact form factor of just one rack unit height, with LAN and USB interfaces.
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Operating wavelength range 1 |
1240 nm to 1650 nm |
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Specification wavelength ranges |
1270 – 1375 nm |
1375 – 1490 nm |
1490 – 1620 nm |
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SOP cycling time 4 (τ90 5) |
< 10 μs |
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Remaining SOP error at input SOP movement rate of 3, 6 |
Typical < 5.5° at 10 rad/s |
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SOP settling time 3, 8 |
Typical < 50 ms |
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Feedback loop time |
Nominal < 150 μs |
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SOP measurement uncertainty 2, 3 |
Typical 1.5° |
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DOP measurement uncertainty 2 |
± 2.0% Typical ± 1.5% |
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Insertion loss including reference connectors |
Typical < 5.0 dB |
Typical < 4.5 dB (1400 – 1460 nm) |
< 4.5 dB (< 4.0 dB at 1550 nm) Typical < 4.0 dB (< 3.5 dB at 1550 nm) |
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Sensitivity of output power to changing the SOP, peak-peak 9 |
Typical < 1.0 dB |
Typical < 0.6 dB |
Typical < 0.4 dB (< 0.2 dB at 1550 nm) |
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Relative output power measure-ment uncertainty due to PDL 9, 10 |
Typical ± 0.1 dB |
Typical ± 0.16 dB |
Typical ± 0.16 dB |
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Relative output power measurement error due to other factors 2 |
Typical ± 0.15 dB |
Typical ± 0.15 dB |
Typical ± 0.15 dB |
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Input power range |
–38 dBm to +19 dBm |
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Maximum safe input power |
+20 dBm |
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1. Range of calibration data.
2. Input power > –20 dBm, averaging time > 10 µs, PDL excluding connector. The polarization analyzer readout reflects the SOP and power at the instrument output. Thus, effects caused by the internal polarization controller are included.
3. DOP = 100%.
4. The instrument adaptively finds the polarization controller settings to let the SOP cycle through user-defined polarization states (closed-loop operation). After having found these settings, the SOP can cycle through the polarization states in open loop operation.
5. Sequence with Stokes vector angles 0° – 90° – 180° – 90° – 0° with 50 kHz. Power range ≥ –10 dBm.
6. Input power > –10 dBm, wavelength 1550 nm, ambient temperature change of max. ± 1K.
7. This value is defined to be 5 times the standard deviation of the angular SOP error on the Poincaré Sphere. During fast SOP variation at the instrument input, rare excursions from the target are to be expected.
8. Time to find target SOP from an arbitrary polarization state.
9. At constant input power and input state of polarization (SOP).
10. Excluding the effect of the internal polarization controller.