In today’s fast-evolving optical communication ecosystem, precision, bandwidth, and format flexibility are non-negotiable requirements for a coherent optical transmitter used in test and measurement. The OMFT Optical Multi-Format Transmitter is a fully integrated optical front-end platform that translates differential electrical RF signals into modulated optical outputs, supporting both single and dual-polarisation transmission across a C-band wavelength range of 1525–1570 nm (191.1–196.25 THz).

What is a dual-polarisation optical multi-format transmitter and why is it needed? A dual-polarisation optical multi-format transmitter is an instrument that takes high-speed electrical I and Q signals (from an AWG, PPG, or DSP system) and converts them into a dual-polarisation IQ-modulated optical signal — simultaneously modulating both the X and Y polarisation states of the optical carrier. This is the signal format used by all modern coherent optical communication systems operating at 100G and above (DP-QPSK, DP-16QAM, DP-64QAM). A dedicated transmitter instrument like the OMFT is needed in test environments because it provides a stable, calibrated, well-characterised reference signal source — unlike the device under test (DUT) transmitter itself, which is what the test is trying to characterise.

What is the electro-optic (EO) bandwidth of the OMFT and why does it determine the maximum baud rate? The electro-optic bandwidth of a coherent transmitter is the frequency range over which the modulator can transfer electrical signal content onto the optical carrier with acceptable fidelity — typically defined as the −3 dB bandwidth of the electro-optic frequency response. The OMFT’s Class 40 variant provides >40 GHz EO bandwidth, supporting baud rates up to 96 GBaud. The Class 60 variant provides 60 GHz, supporting >120 GBaud. The Class 80 variant provides >80 GHz, supporting 170 GBaud — sufficient for 800G single-carrier and research into 1.6T systems. Higher EO bandwidth means the modulator can faithfully reproduce higher-frequency spectral content from the RF input, enabling higher symbol rates without signal distortion.

What is zero-noise mode and how does it protect measurement accuracy? Zero-noise mode is a feature that mutes the ABC’s dither pilot signal — the low-amplitude, low-frequency tone used by the automatic bias control to sense the modulator operating point — after the initial bias lock has been achieved. During the bias search phase, this pilot tone is applied to the modulator bias and its reflection in the optical output is measured to determine the optimal bias setting. Once the bias is locked, zero-noise mode suppresses the pilot entirely, ensuring it does not appear in the modulated optical spectrum and does not interfere with sensitive measurements such as EVM characterisation, spectral shape analysis, or phase noise measurement of the transmitted signal.

Engineered for Next-Gen Optical Modulation

High Electro-Optic Bandwidth — Available in three bandwidth classes to match current and future baud rate requirements: Class 40 (>40 GHz EO bandwidth, 96 GBaud) for 100G and 200G coherent system testing; Class 60 (60 GHz EO bandwidth, >120 GBaud) for 400G system characterisation and coherent receiver qualification; and Class 80 (>80 GHz EO bandwidth, 170 GBaud) for 800G research and next-generation 1.6T system development. All three classes use the same physical chassis and control interfaces — only the modulator component differs.

Automated Bias Control (ABC) — The integrated closed-loop ABC maintains optimal operating points for all modulator sections (I-arm bias, Q-arm bias, phase bias, and DP splitting bias) simultaneously and independently of the RF input modulation format or power level. This eliminates manual alignment, removes bias drift as a source of measurement uncertainty, and enables unattended long-duration test sessions and automated production-line operation without operator supervision.

Zero-Noise Mode — Suppresses the ABC dither calibration signal after the initial bias lock, guaranteeing distortion-free modulated optical output for spectral characterisation, EVM measurement, phase-sensitive testing, and any application where the presence of a sub-modulation pilot tone in the optical spectrum would compromise measurement accuracy.

Flexible Laser Options — The OMFT can be configured with an optional built-in narrow-linewidth integrated laser source for self-contained stand-alone operation, or used with an external tunable laser — including any CoBrite DX, DX2, or MX series laser from the ID Photonics family — for maximum wavelength flexibility, multi-channel coherent testing, and integration into larger system-level test platforms such as the Multi-Terabit Test Solution.

Remote Control and Touchscreen GUI — The OMFT provides complete control via USB, Ethernet, and a built-in web server GUI accessible from any browser without software installation, plus an integrated touchscreen display for direct local operation. This dual-mode control architecture supports hands-on R&D lab use and fully automated production-line deployment within the same instrument.

Device-Specific Calibration Files — Each OMFT unit ships with preloaded device-specific correction files covering gain flatness, phase imbalance, and IQ offset across the full EO bandwidth. These calibration data enable software pre-distortion of the RF input signal to compensate for the individual unit’s electro-optic response — improving modulation linearity, EVM performance, and constellation quality beyond what is achievable with a generic, uncalibrated modulator.

Why It Delivers More

Unmatched Bandwidth for High-Speed Networks

The OMFT Class 80 variant supports symbol rates up to 170 GBaud — covering the baud rate requirements of 800G single-carrier systems and research into 1.6T. With Class 60 supporting >120 GBaud for 400G system validation and Class 40 supporting 96 GBaud for 100G/200G testing, the OMFT family covers the full range of current and near-future commercial coherent network speeds. No manual modification or chassis change is required between classes — select the class at order time based on the maximum baud rate your application requires.

Consistent and Reliable Operation

The closed-loop ABC ensures that modulator bias remains locked to the optimal operating point during repetitive automated test sequences lasting hours or days — with no manual intervention, no format-change recalibration, and no drift-induced measurement variability across test sessions. Zero-noise mode delivers a clean, pilot-free modulated optical signal for coherent experiments where any spectral contamination from the bias control system would compromise measurement validity.

Flexible Integration

The OMFT’s compact 2U 19″ rack chassis, differential 1.85 mm RF connectors, and USB/Ethernet control interfaces make it compatible with the widest range of RF signal sources — including Keysight, Tektronix, and Rohde & Schwarz AWGs and PPGs — and optical measurement instruments including real-time oscilloscopes and the CORX coherent receiver. Its optional external laser input enables direct integration with CoBrite tunable laser sources for wavelength-agile coherent transmitter setups.

Ready for Research and Manufacturing

The OMFT supports the complete range of coherent optical test scenarios: single-carrier coherent receiver characterisation, multi-format interoperability testing, photonic integrated circuit (PIC) transceiver development, BER and Q-factor measurement, and production-line quality control for coherent module manufacturing. Device-specific calibration files accelerate PIC transceiver development cycles by providing a consistent, pre-characterised signal source that removes transmitter-side uncertainty from receiver performance measurements.

Enabler for Digital Twin and DSP Algorithm Prototyping

The OMFT generates hardware-accurate modulated optical signals that closely replicate the signal conditions encountered in real deployed coherent networks — making it the ideal excitation source for digital twin models and DSP algorithm prototyping. Researchers use it to validate DSP carrier recovery, equalisation, and FEC algorithms against real hardware-generated signals rather than software simulations, ensuring that algorithm performance translates correctly from simulation to silicon implementation. It integrates seamlessly with CoBrite tunable lasers, optical filters, and amplifiers in modular testbeds for complete coherent system prototyping.

Coherent Receiver Testing

The OMFT is the reference standard for coherent optical receiver characterisation — providing a stable, well-characterised, high-fidelity DP-IQ modulated signal source whose transmitter impairments are known and controlled. Whether characterising sensitivity at the KP4-FEC threshold, measuring BER vs. OSNR curves, or evaluating coherent receiver DSP performance under various modulation formats, the OMFT ensures that measured receiver performance is genuine device behaviour — not a convolution of transmitter and receiver impairments. Its format-independent ABC means back-to-back QPSK, 16-QAM, and 64-QAM receiver sensitivity measurements can be taken sequentially without any manual transmitter reconfiguration between formats.

Advanced Modulation Format Development

Telecom equipment developers, academic photonics research groups, and national optical laboratories use the OMFT as the hardware transmitter platform for generating and studying advanced coherent modulation formats:

• QPSK (Quadrature Phase Shift Keying) — the standard format for 100G and long-haul coherent systems
• 16-QAM (Quadrature Amplitude Modulation) — deployed in 200G and 400G commercial systems
• 64-QAM and 256-QAM — for ultra-high spectral efficiency in short-reach and metro coherent links
• Probabilistically shaped QAM — for adaptive margin optimisation in next-generation networks
• Nyquist-shaped signals — for sub-channel multiplexing and spectral efficiency research

The OMFT’s Class 80 bandwidth and device-specific calibration enable generation of these formats at baud rates up to 170 GBaud with EVM levels that make it suitable as a golden reference transmitter.

System Design for Multi-Channel Transmission

Supporting both single and dual-polarisation output formats, the OMFT enables realistic emulation of multi-channel coherent transmission scenarios including:

• Characterisation of polarisation-multiplexed DP-QPSK and DP-QAM signals under realistic launch conditions
• Emulation of adjacent-channel interference in DWDM systems — using multiple OMFT units on separate CoBrite laser channels to generate realistic channel-loading conditions
• Testing of wavelength division multiplexing (WDM) components — filters, multiplexers, ROADMs — under realistic modulated signal loading rather than CW laser excitation
• Coherent system BER and Q-factor measurement under varied optical launch power, OSNR, and dispersion conditions

Integration with AWGs and PPGs

The OMFT is designed for direct, low-complexity integration with commercially available Arbitrary Waveform Generators (AWGs) and Pulse Pattern Generators (PPGs) from Keysight, Tektronix, Rohde & Schwarz, and other manufacturers via its standard differential 1.85 mm RF input connectors:

• Inject pre-distorted, probabilistically shaped, or custom constellation signals from an AWG for modulation format research
• Apply standard PRBS-based NRZ or PAM4 signals from a PPG for BER testing at defined symbol rates
• Use DSP-generated, FEC-encoded test patterns for end-to-end coherent link simulation
• Combine with real-time oscilloscopes and the CORX coherent receiver for a complete coherent transmitter-channel-receiver test bench

Optical Component Characterisation

The OMFT is an invaluable reference transmitter for characterising the performance of optical components and subsystems under real modulated signal conditions:

• Optical transceivers and coherent modules — EVM, BER, and OSNR margin characterisation under reference transmitter conditions
• Optical IQ modulators — bandwidth, linearity, EVM, chirp, and extinction ratio measurement using the OMFT as a known-good excitation source
• Amplifiers, filters, and ROADMs — characterisation of their impact on coherent signal quality (EVM degradation, OSNR penalty, spectral distortion) under realistic DP-QAM loading
• Photonic integrated circuits (PICs) — comprehensive electro-optic characterisation during wafer-level and packaged device testing for silicon photonics and InP transceiver development

United Spectrum Instruments is the official authorised distributor for ID Photonics GmbH in India, providing full end-to-end support for the OMFT Optical Multi-Format Transmitter across research institutions, telecom equipment manufacturers, defence establishments, and photonic component companies.

Proven Expertise in Photonics and Optical Instrumentation

With direct experience supporting coherent optical test and measurement deployments across India — including IITs, NITs, DRDO, ISRO, C-DOT, and telecom OEMs — our team brings the application knowledge needed to help customers configure the right OMFT variant, integrate it correctly with their AWG and oscilloscope infrastructure, and extract maximum measurement value from day one:

• Localised technical support — application consultation, integration guidance, and after-sales technical assistance from engineers with hands-on coherent transmitter experience

• Fast lead times — local inventory planning and direct manufacturer relationship enabling shorter delivery windows than direct international procurement

• Integration assistance — hands-on support for connecting the OMFT to AWGs, PPGs, CoBrite lasers, CORX receivers, and real-time oscilloscopes in complete coherent test bench configurations

Access to Global Innovations

Our partnership with ID Photonics GmbH, Germany, ensures Indian customers gain early access to next-generation coherent optical test instruments trusted by global technology leaders — including the OMFT Class 80 platform for 800G and 1.6T research that represents the current frontier of commercial coherent transmitter technology.