Keysight N7781B Datasheet

Keysight N7781B

Polarization Analyzer

Data Sheet

Key features

– Measurement of Stokes parameter (SOP)
– Measurement of degree of polarization (DOP)
– High-speed operation (> 1 MSamples/s)
– Analog output ports for DOP/SOP data
– Robust, no moving parts

Introduction

The Keysight Technologies, Inc. N7781B is a compact high-speed polarization
analyzer that provides comprehensive capabilities for analyzing polarization
properties of optical signals. This includes representation of the state of
polarization (SOP) on the Poincaré sphere (Stokes parameter). The on-board
algorithms together with the on-board calibration data ensure highly accurate
operation across a broad wavelength range.

Due to its real time measurement capability (1 MSamples/s), the instrument is
well suited for analyzing disturbed and fluctuating signals as well as for control
applications requiring real time feedback of polarization information.

Analog data output ports are provided, for example for support of control loops
in automated manufacturing test systems.

The Polarization Navigator software is included and allows a comprehensive
analysis of the obtained measurement data.

03 | Keysight | Polarization Analyzer - Data Sheet

Applications

– Monitoring/measurement of:

– State of polarization (SOP)
– Stokes parameter
– Degree of polarization (DOP)

– High-speed analysis of SOP/DOP of recirculating

signal
– Analysis of PM-ber extinction ratio
– Performance analysis of polarization scramblers
– Intrusion detection

Optical

signal

Amplifier

Amplifier

Amplifier

Amplifier

4 channel

ADC

Trigger in/out

DSP &

Memory

USB

GPIB

Figure 2. Keysight N7781B polarization analyzer setup

Alignment of polarization maintaining bers

N7781B instrument setup and ap-

plication examples

The instrument setup of the N7781B polarization analyzer
is shown in Figure 2. It consists of a unique polarimeter
optics and a high-speed sampling subsystem. The
measurement principle is based on splitting the light into
four sub-beams which are filtered through different polar­izers. The resulting four power levels are evaluated using
on-board calibration data to obtain an accurate SOP- and
DOP-measurement.

Recirculating loop experiments

Managing the polarization properties of the fiber loop is
mandatory for successfully conducting experiments with
such structures. The N7781B high speed polarization
analyzer allows an analysis of the SOP and the DOP of the
circulating signal. The high sampling rate and the trigger
capabilities of the instrument, allow detailed analysis of
the evolution of the SOP and the DOP along each revolu­tion.

N7781B

synchronous

scrambler

Tap coupler

Fiber loop

Amplifier

Pol contr

Accurate alignment of the polarization axis of polarization
maintaining fibers is crucial for the performance of a large
range of optical components. The N7781B, with its high­speed capability, delivers real time feedback regarding
the currently achieved polarization extinction ratio (PER).
It can also be used with the N7783B for automated PER
measurements.

DUT

Swept laser

PMF

GPIB/USB

Computer

Figure 3. Alignment of polarization maintaining fibers

N7781B

polarization

analyzer

GPIB/USB

Event trigger

Advanced communication systems are sensitive to rapid
polarization changes (“events”) on fiber links. Such
events may be caused for example by trains passing by
or by vibrations on bridges. The speed of the polarization
events are of concern for system integrators and network
operators. The event trigger function of the N7781B allows
detecting and recording such events.

Trigger

GPIB/USB

Tx unit Rx unit

Switch

Computer

Figure 1. Recirculating loop experiments

Transmitter

Figure 4. Detecting polarization events

Receiver

N7781B

polarization

analyzer

04 | Keysight | Polarization Analyzer - Data Sheet

Specications 1 - N7781B Polarization Analyzer

Wavelength

Specification wavelength range Opt 300, O-Band 1270 nm to 1375 nm

Opt 400, O/C/L-Band 1270 nm to 1375 nm, 1460 nm to

1620 nm

Opt 500, C/L-Band 1460 nm to 1620 nm

3, 4

2

1260 nm to 1640 nm

1.5°

± 2.0 %

± 0.5 %

3

C/L-Band ± 0.03 dB (± 0.02 dB typical)

O-Band ± 0.07 dB (± 0.04 dB typical)

Operating wavelength range

Polarization analysis

SOP uncertainty (typical)

DOP uncertainty

DOP uncertainty after user calibration
(typical)

3 , 5

3

Maximum sampling rate 1 MHz

Optical power measurement

Relative power uncertainty

Input power range -50 dBm to +7 dBm

Maximum safe optical input power 12 dBm

Ordering instructions

Optical connector options

N7781B-021 Straight contact connectors

N7781B-022 Angled contact connectors

Wavelength options

N7781B-300 1270 nm to 1375 nm

N7781B-400 1270 nm to 1375 nm and 1460 nm to 1620 nm

N7781B-500 1460 nm to 1620 nm

Connector interface

The N7781B should usually be ordered with one 81000xI connector interface, depending on desired connector type. (not
included).

1. Ambient temperature change max. ± 0.5°C since normalization. Specification valid on day of calibration.

2. SOP/DOP measurements are possible outside the specification wavelength range if the user performs a manual calibration.

3. Input power > -30 dBm

4. DOP > 95%

5. User calibration requires a source with DOP = 100% and is valid at fixed wavelength.

05 | Keysight | Polarization Analyzer - Data Sheet

Specications 1 - N7781B Polarization Analyzer (continued)

Accessories

5063-9240 Rack mount kit for 1 unit with filler panel

5063-9212 + 5061-9694 Rack mount parts for 2 units side-by-side

Warranty

Select coverage

Included 3-year warranty (return to Keysight), standard

R-51B-001-5Z 5-year warranty assurance plan (return to Keysight):

Priority warranty service includes one-time coverage for an EOS/ESD
failure.

Calibration

Select Keysight calibration plan

R-50C-011-3 3-year calibration assurance plan (return to Keysight):

Priority calibration service covering all calibration costs for 3 years; 15%
cheaper than buying stand-alone calibrations.

R-50C-011-5 5-year calibration assurance plan (return to Keysight):

Priority calibration service coveringall calibration costs for 5 years; 20%
cheaper than buying stand-alone calibrations.

General characteristics

Dimensions (D x W x H) 380 mm x 213 mm x 88 mm

(excluding front and back rubber cushions and handle)

Weight Approx. 4 kg

Recommended recalibration period 24 month

Operating temperature +5 °C to +40 °C

Operating humidity 0% to 80%, non-condensing

Altitude The maximum operating altitude is 2000 m.

Pollution protection Pollution degree 2.

Warm-up time 20 minutes

Interfaces The instruments can be controlled via USB or GPIB interfaces

Power consumption Line power: AC 100 to 240 V ± 10%, 50/60 Hz, 60 VA max.

06 | Keysight | Polarization Analyzer - Data Sheet

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(BP-07-10-14)

This information is subject to change without notice.
© Keysight Technologies, 2013 - 2014
Published in USA, August 3, 2014
5989-6938EN

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