ID OSA Optical Spectrum Analyser for Coherent LiDAR

Why Coherent LiDAR Needs Spectral Checks

Coherent LiDAR measures range and velocity by mixing the light returned from a target with a copy of the light that was sent. The result depends on the laser: it has to sit at the intended wavelength, with clean side modes, and its amplified output has to stay spectrally clean as power is raised for longer range.

Most coherent LiDAR work in fibre uses the 1550 nm region, where tunable lasers, erbium amplifiers and coherent receivers are well established. A typical development bench therefore holds a laser, often a booster amplifier and a coherent receiver, and each part can change the spectrum the next one sees.

Some properties need dedicated methods. Laser linewidth, phase noise and chirp linearity are measured with interferometric or coherent techniques, not with a spectrum analyser. What an OSA adds is a fast, accurate view of where the power sits across the band.

The Optical Spectrum Analyser on a LiDAR Bench

The ID OSA optical spectrum analyser from ID Photonics measures by coherent detection. Incoming light is mixed with an internal tunable laser reference and the spectrum is rebuilt from the result, instead of being scanned by a grating. The design is solid state, with no moving optical parts.

On a coherent LiDAR bench it confirms the source’s centre wavelength against its target, shows side modes and spurious lines, and checks the spectrum after the booster amplifier, so problems are found before the system is put together.

Why Accuracy, Power Range and Speed Matter

Three figures decide how useful the analyser is on a LiDAR bench:

• Frequency accuracy: ±1 GHz (±8 pm), to confirm the source sits where the receiver and filters expect it.
• Power range: −30 to +23 dBm on the standard port for boosted outputs, and −60 to +3 dBm on the high-sensitivity port for taps.
• Speed: a full band sweep in 0.5 s, so the spectrum can be checked each time a setting changes.

Built for Coherent LiDAR Development

The ID OSA is a half-width 19-inch unit weighing 1.8 kg, which fits development benches and test racks.

Resolution

Spectral sampling is 2.5 pm, with a 1.7 GHz (13.6 pm) 3 dB bandwidth, enough to separate the main line from nearby side modes and spurious lines.

C-band and L-band

The C-band covers 1528.5 to 1567.5 nm and the L-band 1569.08 to 1609.73 nm, which covers the 1550 nm region used by fibre-based coherent LiDAR.

Triggered sweeps

A 3.3 V TTL trigger in and out lets sweeps start in step with laser settings, amplifier changes or other instruments on the bench.

Automation

USB, Ethernet, a browser GUI and SCPI commands for Python, LabVIEW and MATLAB let spectral checks run inside automated LiDAR test sequences. Optical return loss is above 35 dB.

Building a Complete Coherent LiDAR Bench

The Narrow Linewidth Tunable Laser Source provides the LiDAR carrier, and the Dual-Port Tunable Laser Source gives two independent outputs for set-ups that need a second wavelength. The Polarisation-Maintaining EDFA boosts the transmit power in the C-band, and the optical spectrum analyser checks the amplified output on its +23 dBm port. The CORX Coherent Optical IQ Receiver detects the mixed return signal for analysis. Checking the spectrum before and after the amplifier, and again at the receiver input, shows at which point in the chain any unwanted line or shift first appears.

Who Uses It

• Automotive and industrial LiDAR developers
• Fibre sensing and coherent ranging research teams
• Laser and amplifier makers supplying LiDAR programmes
• Defence and aerospace sensing laboratories
• Photonics groups at IITs and national research institutes

Supply and Support in India

United Spectrum Instruments (USI), Chennai, supplies the ID OSA optical spectrum analyser in India as the distributor for ID Photonics, together with the CoBrite lasers, the CORX receiver and the PM EDFA.

USI helps coherent LiDAR teams choose the band, set up port use and fit the analyser into automated tests, and provides installation, training and after-sales support, with calibration and servicing coordinated with ID Photonics.

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:

• Your LiDAR wavelength and band
• The sources and amplifiers you need to check
• The power levels at the point of measurement
• Your test software and bench set-up