Keysight N7785B Datasheet

Keysight Technologies
N7785B
Synchronous Scrambler

Data Sheet

Introduction

The Keysight Technologies N7785B is a high-speed synchronous scrambler. It contains a polarization con­troller plus microcontroller-based driving circuitry. This unit can operate in various modes:

As a synchronous scrambler, the device switches the SOP of the output signal in a random (pseudo) way.
Switching of the SOP occurs within a few microseconds.

The SOP is stable for a predefined time until it again switches to a new SOP.

An electrical trigger input can be used to synchronize the scrambler with external events.

As an SOP switch the N7785B allows switching the internal waveplates to user definable angles with very
high speed and repeatability.

As a traditional scrambler, the Keysight N7785B varies the output SOP smoothly in a random/pseudo
random way.

The unit does not contain any moving parts, and therefore is robust and withstands even rough environmental
conditions.

All above-mentioned applications of the N7785B are supported by Keysight’s PC software package which
comes with this instrument.

Key benets

– Comprehensive polarization control and management capabilities.
– Covers S-, C-, and L-band plus 1.3 μm window.
– Compact size.
– Robust, no moving parts.
– PC software package included

03 Keysight N7785B Synchronous Scrambler

Key benets

– Comprehensive polarization control and management

capabilities.

– Covers S-, C-, and L-band plus 1.3 μm window.
– Compact size.
– Robust, no moving parts.

Applications

– Recirculating loop experiments: loop-synchronous

polarization scrambling.

– System test: polarization sensitivity analysis on link/

transmission quality.

– Characterization of optical components.

Keysight N7785B instrument setup and
application examples

SMF

Power in

Figure 2. N7785B instrument setup.

The instrument setup is shown in Figure 2. The LiNbO3

polarization controller is controlled by a signal processor

which supplies user-denable sequences to the
polarization controller. In this way, the SOP can be

controlled in steps but also continuously. The trigger
system provides synchronization capabilities to external
digital signals.

LiNbOз

polarization controller

Microcontroller board

SMF

Trigger in

Trigger out

USBGPIB

The results obtained in re-circulating loop experiments
depend heavily on the PMD and PDL properties of the
loop. Loop synchronous polarization scrambling schemes
have proven to be necessary for generating results
comparable to deployed systems.

The synchronized scrambling feature of the N7785B
is a unique enhancement to conventional polarization
scramblers. The polarization can be scanned according
to a pseudo-random but reproducible path. Instead of a

continuously changing SOP, the SOP is switched in
discrete steps that are synchronized with an input or
output trigger signal. After switching, a stable SOP is
quickly reached and held until the next step.

The N7785B is ideally suited to provide the synchronous
scrambling capability in such experiments.

This is a key capability for providing realistic change of
polarization from cycle to cycle around the loop, while
providing a stable SOP during passage of the bit train

through the scrambler. This avoids the unrealistic effect
rapid change of the polarization during the bit train
caused by continuous scramblers.

Polarized

source

Figure 4. Scrambling/depolarization.

N7785B

synchronous

scrambler

DOP < 5%

Light emitted by a laser is typically highly polarized. In
order to avoid polarization effects it is common in some
applications to depolarize light. This can be achieved
highly effectively using the N7785B synchronous
scrambler unit.

N7785B

synchronous

scrambler

Trigger

Figure 3. Recirculating loop.

Amplifier

Tx unit Rx unit

Fiber loop
Pol contr

Switch

04 Keysight N7785B Synchronous Scrambler

Specications 1 N7785B Synchronous Scrambler

Wavelength

Operating wavelength range 1260 nm to 1640 nm

Polarization control

SOP switching time < 10 μs

Optical power

PDL (typical) C/L-Band < 0.2 dB

O-Band < 0.5 dB
Insertion loss < 3.5 dB (< 3 dB, typical)
Maximum safe input power 20 dBm

Ordering instructions

Optical connector options

N7785B-021 Straight contact connectors
N7785B-022 Angled contact connectors

Connector interface

The N7785B should usually be ordered with two 81000xI connector interfaces, depending on desired connector type
(not included).

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 months
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.

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

Keysight | N7785B Synchronous Scrambler Data Sheet

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(BP-04-23-14)

This information is subject to change without notice.
© Keysight Technologies, 2013 - 2014
Published in USA, August 3, 2014
5989-8114EN

www.keysight.com