Polarisation-Maintaining EDFA for Defence & Secure Communication

Why Secure Communication Test Beds Need Polarisation-Stable Amplification

Coherent links used for secure communication carry information in the phase and polarisation of the light, not just its power. In a test bed, signals often need amplifying: to make up for the loss of a multiplexer, to drive a long fibre spool or to bring a weak signal up to a receiver’s working level.

A standard erbium-doped amplifier boosts the power but lets the polarisation state wander. For a polarisation-sensitive modulator, interferometer or coherent receiver further down the bench, that wandering has to be corrected before results can be trusted. An amplifier that keeps the polarisation fixed removes that correction step.

Defence and secure communication teams also run the same bench many times as they change modulation formats, fibre lengths or receiver settings. Holding the polarisation fixed through the amplifier means each run starts from the same conditions, so changes in the results come from the change being tested, not from the amplifier.

The Polarisation-Maintaining EDFA on the Bench

The polarisation-maintaining EDFA amplifies C-band signals from 1530 to 1565 nm on PM1550 PANDA fibre, with FC/APC connectors aligned to the slow axis. Light that enters on the slow axis leaves on the slow axis, with a polarisation extinction ratio of at least 20 dB.

The same amplifier can be placed as a booster after a transmitter or multiplexer, as an in-line amplifier on a fibre spool, or as a pre-amplifier ahead of a receiver, depending on what the secure communication test bed needs.

Because the amplifier covers 1530 to 1565 nm, the lasers and channels that pass through it should be tuned inside that range. Wider-band sources on the same bench can still be used for stages that do not go through the amplifier.

Why Gain, Noise Figure and PER Matter

Three figures decide how much the amplifier helps the rest of the bench:

• Gain and output power: small-signal gain of at least 25 dB and up to +23 dBm saturated output make up for multiplexer and fibre losses.
• Noise figure: 5 dB or less limits how much noise the amplifier adds to the signal it boosts.
• Polarisation extinction ratio: at least 20 dB, typically about 23 dB, keeps the output on the intended axis.

Built for Defence and Secure Communication Labs

Four further specifications decide how the PM EDFA fits into a lab bench.

Input range

Input power from −6 to +3 dBm covers the outputs of tunable lasers and multiplexers used on coherent test benches.

Isolation

Input and output isolation above 35 dB keeps reflections from the rest of the bench out of the amplifier.

Remote control

RS-232 control comes as standard, with Ethernet as an option, so the amplifier can be set and monitored from test software. This lets gain and output be logged alongside the other instruments during long or repeated test runs.

Operating range

The amplifier operates from −5 to +35 °C, which suits air-conditioned labs and test rooms.

Building a Complete Secure Link Test Bed

A polarisation-maintained carrier comes from the Narrow Linewidth Tunable Laser Source, or several channels are combined by the Polarisation-Maintaining Multiplexer. The polarisation-maintaining EDFA then makes up for the multiplexer and fibre losses. The ID OSA Optical Spectrum Analyser checks the amplified spectrum, and the CORX Coherent Optical IQ Receiver measures the signal quality after amplification. Comparing CORX results with and without the amplifier in place shows how much the amplification stage affects the link.

Who Uses It

• Defence research and development laboratories
• Secure network and communication system developers
• Coherent transceiver and LiDAR research teams
• Fibre sensing and interferometry groups
• Photonics groups at IITs and national research institutes

Supply and Support in India

United Spectrum Instruments (USI), Chennai, supplies the polarisation-maintaining EDFA in India, together with the ID Photonics narrow linewidth laser and ID OSA, the CORX receiver and the PM multiplexer.

Sourcing the test bed from one supplier gives secure communication teams a single point of contact for amplifier placement, connector alignment, installation and after-sales support, with pre-sales guidance on matching gain and output power to the rest of the bench.

Request a Configuration

Download the brochure from this page, use the Enquire Now button, write to sales@unitedspectrum.in, or call +91 93631 83748 / +91 97899 04948. Please mention:

• Where the amplifier will sit: booster, in-line or pre-amplifier
• The input power and the output power you need
• The number of channels to be amplified
• Your connector type and control interface