The PMUX is a next-generation optical signal combiner specifically designed for Dense Wavelength Division Multiplexing (DWDM) test environments requiring polarisation preservation at every wavelength channel. It integrates a polarisation-maintaining AWG (PM-AWG) built using PANDA-type PM fibre throughout the internal waveguide and connection structure, ensuring stable, interference-free, polarisation-maintained transmission across all channels from individual laser inputs to the combined multiplexed output.

What is a polarisation-maintaining AWG (PM-AWG) and how does it differ from a standard AWG? A standard arrayed waveguide grating (AWG) multiplexer combines multiple wavelength channels onto a single output fibre using diffraction in a planar waveguide array. It provides wavelength selectivity and low insertion loss but does not control the polarisation of the combined channels — the output polarisation state depends on the input polarisation, the waveguide birefringence, and the environmental conditions, and varies from channel to channel and over time. A PM-AWG uses PANDA-geometry PM fibre and PM-compatible waveguide connections throughout, maintaining a polarisation-preserving signal path for each channel from its individual input to the multiplexed output. This ensures that all channels emerge from the combined output with the same, well-defined, stable linear polarisation alignment — essential for downstream MZM modulation and coherent receiver compatibility.

What is the difference between 50 GHz and 100 GHz channel spacing, and which should I choose? Channel spacing defines the frequency separation between adjacent DWDM channels on the ITU-T G.694.1 grid. 100 GHz spacing (approximately 0.8 nm at 1550 nm) is the original DWDM standard, supporting 40 channels across the C-band. 50 GHz spacing doubles the channel count to 80 channels in the same bandwidth — enabling higher aggregate capacity but requiring tighter laser frequency accuracy and narrower filter passbands (0.55 nm 3 dB bandwidth for 100 GHz in the PMUX). Choose 100 GHz for most standard DWDM component testing, system emulation, and telecom research where compatibility with widely deployed network infrastructure is the priority. Choose 50 GHz when emulating high-capacity next-generation DWDM systems or testing components specified for 50 GHz grid deployment.

What is the PMUX’s role within a complete coherent DWDM test platform? Within a complete coherent optical test platform, the PMUX sits between the individual tunable laser sources (CoBrite MX or DX series) and the downstream optical modulator array or device under test. It receives individual CW laser channels on separate PM input fibres, combines them onto a single PM output fibre with ITU-T grid alignment, polarisation preservation, and <6 dB insertion loss — and delivers the combined multi-channel, PM-maintained comb signal to the input of a modulator, amplifier, or optical network element under test. The PMUX’s role is analogous to the frequency combiner in a DWDM transmitter line card — but implemented as a test-grade, characterised PM-AWG rather than a production-grade passive component.

This state-of-the-art system is ideal for users requiring low insertion loss, high extinction ratios, and consistent polarisation across large channel counts. The PMUX is ideal for:

• Creating high-density 50 GHz and 100 GHz ITU-T DWDM channel combs with polarisation-maintaining output
• Emulating real-world C-band DWDM network spectral loading in a controlled laboratory environment
• Testing optical amplifiers, transponders, coherent receivers, and network elements under realistic multi-channel signal conditions
• Developing and verifying new DWDM network architectures with accurate channel count and spacing emulation

High-Performance DWDM Channel Grid Generation

The PMUX supports both 50 GHz and 100 GHz ITU-T G.694.1 channel spacing configurations, enabling generation of stable, dense DWDM wavelength combs for rigorous multi-channel optical system testing. Channel centre offset is held to ±0.04 nm — ensuring each combined channel is precisely aligned to the ITU-T grid frequency with accuracy sufficient for coherent receiver channel selection and ROADM passband alignment. The 3 dB passband of 0.55 nm (at 100 GHz spacing) provides adequate margin for CoBrite laser frequency accuracy while maintaining adequate adjacent-channel isolation for low-crosstalk multi-channel operation.

Polarisation-Maintaining Architecture

The PMUX uses PANDA PM fibre and PM-compatible AWG waveguide connections throughout the complete signal path — from each individual channel input connector to the multiplexed output connector — preventing polarisation-dependent loss, polarisation crosstalk between channels, and polarisation state evolution that would otherwise occur in a standard AWG. The ≥16 dB PER (typically 20 dB) at the multiplexed output ensures that all channels arrive at the downstream MZM or test device with a consistent, well-aligned linear polarisation state, which is essential for modulation format testing with QPSK, 16-QAM, 64-QAM, and higher-order coherent formats.

Flexible Grid Configurations

Available in both fixed grid and flexible grid configurations — selectable at time of order. Fixed grid configurations provide standard 50 GHz or 100 GHz ITU-T channel spacing across the specified channel count. Flexible grid configurations allow non-uniform channel spacing and sub-50 GHz channel allocation for testing next-generation elastic optical network (EON) architectures and super-channel transmission systems. Flexible grid operation eliminates the need for costly wavelength-selective switches (WSS) or tunable filters in the channel comb generation path — simplifying the test setup and reducing total system cost significantly for multi-channel coherent research setups.

Autonomous, Maintenance-Free Operation

The PMUX is fully autonomous after power-up — requiring no periodic recalibration, no moving optical components, and no ongoing manual adjustment. Its solid-state PM-AWG architecture delivers reliable 24/7 continuous operation, making it suitable for unattended long-duration production test runs, automated overnight measurement sequences, and always-on optical network emulation setups. The AWG passband centre frequencies and PER are stable with temperature across the 0–50°C operating range without active temperature control or periodic realignment.

Rack-Mountable Industrial Design

Standard 19-inch rack compatible chassis (100 × 460 × 540 mm) fits neatly into optical test lab and production test racks alongside CoBrite MX laser mainframes, PM EDFAs, OMFT transmitters, and CORX receivers. The rugged construction — designed for continuous operation in both controlled laboratory and thermally variable factory environments — ensures long-term mechanical stability of the PM fibre connections and AWG waveguide alignment without performance degradation.

Seamless Integration with CoBrite MX Lasers

The PMUX is specifically optimised for plug-and-play integration with CoBrite MX and CoBrite DX series tunable laser sources — the PMUX input channel spacing and connector configuration are matched to the CoBrite MX output channel layout, enabling direct connection without intermediate fibre routing, polarisation alignment, or power level adjustment. When connected to a CoBrite MX configured with N laser channels, the PMUX immediately provides an N-channel, ITU-T grid-aligned, PM-maintained DWDM comb at its output — requiring only a single USB connection to the Windows GUI for system status monitoring.

Windows-Based GUI for Easy Monitoring

The PMUX includes a Windows-compatible GUI accessible via USB interface for real-time system status monitoring, channel power readout, control configuration, and diagnostic access — with no additional drivers required for standard Windows environments. The interface provides per-channel input power monitoring and combined output power readout, enabling quick verification of correct laser-to-channel assignment and detection of any connector or fibre fault before beginning a test sequence.

DWDM Transport Testing

The PMUX is the standard front-end component for DWDM transport layer testing — enabling simulation of realistic DWDM channel loading environments that replicate the spectral conditions encountered in deployed C-band DWDM networks. Test engineers use the CoBrite MX + PMUX combination to generate controlled, ITU-T grid-aligned multi-channel signal loads for testing:

• Optical transponders and coherent transceivers — measuring BER, Q-factor, and OSNR margin under realistic adjacent-channel loading at 50 GHz or 100 GHz channel spacing
• Optical amplifiers (EDFAs, Raman) — characterising gain flatness, noise figure, and saturation behaviour under full C-band channel loading conditions that match real network amplifier operating points
• Fibre links and dispersion compensation systems — evaluating nonlinear impairment accumulation, chromatic dispersion tolerance, and ROADM cascade penalties under realistic multi-channel signal loading

Optical Network Simulation

The PMUX is indispensable for simulating multi-wavelength optical network environments under controlled laboratory conditions — enabling research and development of next-generation optical network technologies without access to a deployed network:

• Network research labs studying spectral efficiency, adaptive modulation, and elastic optical networking using realistic multi-channel signal environments
• Next-generation optical switch and ROADM development — testing wavelength-selective switching, channel add/drop, and optical cross-connect performance under realistic DWDM loading
• Passive and active optical component qualification — validating insertion loss, channel isolation, polarisation-dependent loss (PDL), and crosstalk under true multi-channel signal conditions rather than CW single-channel excitation

Modulation Format Testing

When combined with a CoBrite MX tunable laser mainframe providing up to 48 independently controlled laser channels, the PMUX enables a complete multi-channel coherent DWDM transmitter platform where every channel can be independently modulated:

• Generate modulated DWDM combs across all active channels simultaneously, with each channel carrying an independently controlled modulation format (QPSK, 16-QAM, 64-QAM, or unmodulated CW)
• Evaluate signal quality metrics (EVM, Q-factor, BER) across all channels under realistic inter-channel crosstalk and nonlinear loading conditions
• Perform high-fidelity coherent transmission testing for next-generation 400G and 800G DWDM system validation at IITs, NITs, DRDO research centres, and telecom OEM test labs across India

Optical Component Manufacturing

The PMUX is used for automated production testing of optical components and modules where multi-channel polarisation-maintaining signal inputs are required to characterise device performance under realistic operating conditions:

• Coherent modulators and OMFT transmitters — verifying modulation efficiency, PER at output, and EVM uniformity across all DWDM channels under simultaneous multi-channel excitation
• Coherent transceivers and WDM transponders — measuring insertion loss, wavelength accuracy, OSNR sensitivity, and BER performance across all channels in parallel rather than sequentially
• Wavelength-specific optical components (filters, AWGs, ROADMs) — characterising passband shape, channel isolation, and polarisation-dependent loss under full DWDM channel loading that reflects real deployment conditions

High Channel Count Simulation

For applications requiring 40, 80, or 100+ simultaneous DWDM channel emulation — including wideband amplifier characterisation, next-generation ROADM validation, and submarine cable system testing — the PMUX handles ultra-high-density channel grids with:

• Minimal power variation across channels (1–1.5 dB band uniformity)
• Tight channel centre frequency tolerances (±0.04 nm) aligned to the ITU-T G.694.1 grid
• Exceptional repeatability session-to-session and unit-to-unit — critical for production-line yield analysis and long-term R&D measurement consistency

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As India’s official authorised channel partner for the PMUX, United Spectrum Instruments ensures full local support, competitive pricing, and expert consultation for every customer — from research institutions evaluating the PMUX for the first time to telecom OEMs integrating it into production test lines.

Superior Polarisation Control

Essential for advanced optical modulation formats and coherent signal integrity — the PMUX’s ≥16 dB PER (typically 20 dB) across all channels simultaneously is the specification that makes reliable multi-channel MZM modulation and coherent receiver testing possible. United Spectrum engineers can advise on connector type selection (FC/APC vs FC/PC), slow-axis alignment verification, and PER measurement procedures to ensure the PMUX performs to specification in your specific installation.

• Scalable Testing with Minimal Complexity — The CoBrite MX + PMUX combination replaces what would otherwise require individually routed PM fibre channels, separate polarisation controllers, and manual channel-by-channel alignment — saving setup time, reducing cost, and eliminating operator-dependent polarisation adjustment errors in complex multi-channel test setups.

• Reliability You Can Trust — Built for continuous 24/7 use in test labs, R&D centres, and telecom production environments, the PMUX’s maintenance-free solid-state PM-AWG architecture delivers consistent performance over years of operation without recalibration.

• Seamless Workflow with CoBrite MX — Plug-and-play integration with CoBrite MX laser mainframes and CoBrite DX series sources saves engineers time and eliminates alignment errors in complex coherent DWDM test setups — a validated, characterised system-level integration that United Spectrum Instruments supports end-to-end.

Local Support in India — Access pre-sales consultation (channel count, spacing, grid configuration), post-sales technical support (connector alignment, PER verification, system integration), and fast delivery through United Spectrum Instruments across India.