Coherent Optical Receiver
Turn-Key Coherent Optical Receiver for Oscilloscope-Based Testing
The CORX Coherent Optical Receiver is a fully integrated, turn-key coherent receiver instrument designed...
Coherent Optical Receiver
Precision Reception for High-Speed Optical Signals with Coherent Optical Receiver (CORX)
Turn-Key Coherent Optical Receiver for Oscilloscope-Based Testing
The CORX Coherent Optical Receiver is a fully integrated, turn-key coherent receiver instrument designed to interface seamlessly with any real-time oscilloscope through four single-ended RF output channels. By optically mixing the incoming test signal with a built-in, continuously tunable local laser oscillator (LO), the CORX enables precise coherent detection of dual-polarisation, IQ-modulated optical signals — without requiring external laser sources, separate polarisation-diversity components, or additional RF amplifiers.
This architecture makes the CORX an ideal reference receiver for advanced coherent optical communication testing, where signal integrity, phase accuracy, and measurement repeatability are non-negotiable. Engineers connect four SMA RF outputs directly to a real-time oscilloscope, capture the full in-phase (I) and quadrature (Q) signal content across both polarisations simultaneously, and proceed immediately to DSP-based analysis — all from a single 1U instrument.
Key performance fact: The CORX supports baud rates beyond 120 GBaud on the 60 GHz variant — making it one of the highest-bandwidth integrated coherent receiver instruments available for oscilloscope-based testing in India today.
High-Fidelity C-Band IQ Signal Analysis
Optimised for full C-band operation (1528–1568 nm / 190.70–196.65 THz), the CORX supports accurate characterisation of IQ-modulated optical signals across all dual-polarisation coherent modulation formats currently deployed in commercial and research optical networks. It is specifically engineered for:
- Transmitter characterisation — measuring IQ skew, phase noise, modulation linearity, and constellation quality of coherent optical transmitters and IQ modulators
- Performance benchmarking — quantifying EVM (error vector magnitude), optical signal-to-noise ratio (OSNR), and BER-related metrics against ITU-T G.975 and OIF CEI standards
- Coherent signal analysis — capturing and post-processing full dual-polarisation IQ waveforms for DSP development, algorithm validation, and modulation format research
The CORX’s stable, repeatable detection performance — with ±3 ps IQ skew and ±5 ps XY polarisation skew — ensures reliable, consistent results across extended measurement sessions in DWDM systems, coherent transceiver qualification, and photonics R&D laboratories.
Understanding Coherent Optical Receiver
The CORX is a 20/40/60 GHz dual-polarisation IQ coherent receiver with an integrated tunable local oscillator (LO), integrated transimpedance amplifiers (TIAs), and a built-in variable optical attenuator (VOA) — providing a complete optical-to-electrical conversion front-end for real-time oscilloscopes.
What is a coherent optical receiver? A coherent optical receiver is an instrument that recovers the amplitude, phase, and polarisation state of an incoming modulated optical signal by mixing it with a reference local oscillator laser in a balanced photodetector arrangement. Unlike direct-detection receivers (which measure only optical power), coherent receivers capture the full complex field — enabling detection and demodulation of phase-modulated formats such as QPSK, 8-PSK, 16-QAM, 64-QAM, and beyond. The CORX performs this function for both X and Y polarisations simultaneously, delivering four RF outputs (XI, XQ, YI, YQ) for direct connection to a real-time oscilloscope.
What makes the CORX a “turn-key” system? Most oscilloscope-based coherent test setups require a separate tunable laser as the local oscillator, a polarisation-diversity optical hybrid, balanced photodetectors, and RF amplifiers — assembled and aligned individually. The CORX integrates all of these into a single 1U chassis: built-in tunable LO (190.70–196.65 THz), polarisation-maintaining 90° optical hybrid, balanced photodetectors, and four TIA-amplified RF outputs — eliminating setup complexity and ensuring consistent performance from the first measurement.
What modulation formats does the CORX support? The CORX supports coherent detection and analysis of QPSK, 8-PSK, 16-QAM, 64-QAM, and higher-order dual-polarisation modulation formats used in 100G, 200G, 400G, 800G, and beyond. It is compatible with all standard dual-polarisation coherent formats defined by OIF and ITU-T for commercial and research optical networks.
Technical Specifications
Bandwidth Variants
- 20 GHz, 40 GHz, 60 GHz (user selectable at time of order)
RF Specifications
- Low Frequency Cutoff: 1 MHz
- RF Output Swing: 600 mV
- Output Impedance: 50 Ohm
- Total Harmonic Distortion (THD): <5%
- RF CMRR: -20 dBe
- IQ Skew: ±3 ps
- XY Polarisation Skew: ±5 ps
Optical Specifications
- Wavelength Range: 1528 – 1568 nm (C-Band)
- Polarisation Extinction Ratio (PER): >17 dB
- Return Loss (at 1550 nm): 27 dB
- Responsivity: 0.035 A/W
- Variable Optical Attenuator (VOA): 10 dB
Local Oscillator Specs
- Frequency Range: 190.70 – 196.65 THz
- Linewidth: <100 kHz (25 kHz typical)
- Frequency Accuracy: ±0.3 GHz over 24 hours
- Output Power: 10–16 dBm
- Fibre Type: PM PANDA with PER > 20 dB
Connectivity & Control
- Interfaces: USB, Ethernet
- Control: SCPI commands, Built-in web server
- GUI: Web browser GUI (Chrome, Firefox, Edge)
Mechanical & Electrical
- Dimensions: 365 × 45 × 275 mm
- Weight: 3 kg
- Power Supply: 100–240 VAC, 1A, 50/60 Hz
Power Consumption: 80W
Key Features and Advantages
High-Bandwidth Dual-Polarisation Reception
- Available in 20 GHz, 40 GHz, and 60 GHz bandwidth versions to match current and future baud rate requirements
- Dual-polarisation support captures the full X and Y polarisation IQ content simultaneously — essential for DP-QPSK, DP-16QAM, DP-64QAM and higher-order dual-polarisation formats
- Excellent phase accuracy with ±3 ps IQ skew and ±5 ps XY polarisation skew ensures reliable constellation measurements with minimal instrument-induced distortion
Ideal for characterising modulated signals with high spectral efficiency in real time, from 100G research to 800G+ production qualification.
Built-In Tunable Local Oscillator (LO)
- C-Band LO tunable across 190.70–196.65 THz (1528–1568 nm) — full C-band, ITU-T G.694.1 grid aligned
- Linewidth: <100 kHz (25 kHz typical) — sufficient for QPSK, 16-QAM, and higher-order coherent formats
- Output Power: 10–16 dBm, tunable in 1 MHz steps
- PM PANDA fibre output with PER >20 dB — polarisation-maintaining from LO to optical hybrid
The integrated LO eliminates the need for a separate external tunable laser source, simplifying setup, reducing bench footprint, and ensuring guaranteed phase-coherent signal mixing across the full C-band without additional alignment or calibration.
Integrated Transimpedance Amplifiers (TIAs)
Each of the four IQ output channels (XI, XQ, YI, YQ) features a high-speed integrated TIA delivering:
- 600 mV RF output swing — sufficient for direct connection to standard real-time oscilloscope input channels without additional RF amplification
- 50 Ohm output impedance — direct compatibility with SMA-input oscilloscopes, digitisers, and ADCs
- Low distortion: <5% THD — preserves signal linearity for accurate constellation analysis and EVM measurement
- Support for low-power optical input signals with built-in VOA (10 dB) for optimised detector loading
Web-Based GUI and Remote Automation
- Browser-based GUI accessible via Ethernet from any PC, tablet, or smartphone — no software installation or drivers required
- USB and Ethernet dual connectivity with full SCPI command compatibility for programmatic control
- Supports complete automation with Python (PyVISA), LabVIEW (NI-VISA), MATLAB (Instrument Control Toolbox), and custom test frameworks
- Built-in web server enables multi-user network access and remote lab management without dedicated control hardware
Compact, Rack-Mountable Design
- 1U (1 HE) chassis: 365 × 45 × 275 mm — fits standard 19″ racks in telecom labs, university photonics labs, and production test environments
- Weight: 3 kg — portable and easy to reposition between test setups
- Single-cable power: 100–240 VAC input, fully compatible with Indian 230V/50Hz standard power supply
Applications Across Industries
Optical Front-End for Real-Time Oscilloscopes
The CORX provides a complete, integrated coherent receiver interface for any real-time oscilloscope, enabling phase- and amplitude-resolved capture of high-speed optical signals without external optical hybrids, balanced detectors, or RF amplifiers:
- Captures full dual-polarisation IQ waveforms (XI, XQ, YI, YQ) simultaneously for complete signal characterisation
- Enables phase- and amplitude-resolved analysis of QPSK, 8-PSK, 16-QAM, 64-QAM, and higher-order coherent formats
- High-fidelity RF outputs with 600 mV swing and 50 Ohm impedance connect directly to oscilloscope input channels for immediate signal capture and DSP post-processing
DWDM Transmission and Receiver Testing
The CORX’s continuously tunable built-in LO — covering the full C-band ITU-T G.694.1 grid — makes it the natural instrument for channel-by-channel validation of DWDM transmission systems and coherent receivers:
- Validates multi-channel DWDM link performance including per-channel OSNR, BER, and constellation quality
- Characterises coherent detection and demodulation performance of commercial coherent transceivers and modules
- Measures channel selectivity, frequency accuracy, and adjacent-channel interference in DWDM systems from 100G to 800G
Advanced Modulation Format Testing
- Full IQ signal separation with linear, low-distortion output response enables accurate EVM, phase error, and constellation quality measurement
- Supports modulation format development and BER analysis for QPSK, 16-QAM, 64-QAM, and beyond
- Suitable for both lab-grade research environments (algorithm development, format comparison) and production testing lines (transceiver qualification to OIF and ITU-T standards)
Reference Receiver for Optical Component Characterisation
The CORX serves as a high-fidelity reference receiver for characterising the performance of transmitter-side and modulation-side optical components:
- Testing optical IQ modulators — measuring IQ imbalance, phase error, extinction ratio, and chirp
- Characterising DAC and DSP-driven optical transmitters — measuring linearity, frequency response, and SNR
- Evaluating optical filters, amplifiers, and passive components in the signal path for their effect on coherent signal integrity
- Verifying compliance with coherent interface standards (OIF, ITU-T G.975, IEEE 400G) at component and subsystem level
DSP Algorithm Development and Validation
Research institutions and coherent system developers use the CORX as the measurement front-end for DSP algorithm development and real-time validation:
- Captures raw IQ waveforms for offline DSP simulation and algorithm refinement in MATLAB or Python
- Enables real-time DSP validation by feeding oscilloscope-captured IQ data directly into software-defined coherent receiver implementations
- Supports carrier recovery, equalisation, and forward error correction (FEC) algorithm benchmarking under real optical signal conditions
- Ideal for academic photonics research groups at IITs, NITs, and national optical laboratories developing next-generation coherent DSP techniques.
Why Choose United Spectrum Instruments?
United Spectrum Instruments is the official authorised distributor of the CORX Coherent Optical Receiver in India, providing complete pre-sales and post-deployment support for telecom OEMs, photonics research institutions, defence establishments, and production test laboratories across the country.
What you get when you buy through United Spectrum:
- Wide bandwidth options (20 / 40 / 60 GHz) — future-proof your test capability from 100G through to 800G+ systems with the right bandwidth variant for your current and planned requirements
- Integrated tunable LO — no need for an external laser source; the CORX is self-contained and ready to measure immediately on arrival
- Built-in TIAs — clean, amplified 600 mV RF outputs connect directly to your oscilloscope input channels without additional RF hardware
- Browser-based GUI and SCPI — remote control and full automation support from day one, with no software licensing costs
- 1U compact design with full C-band coverage — fits any standard lab or telecom rack, fully compatible with Indian 230V/50Hz power infrastructure
- Backed by United Spectrum Instruments’ in-country support — application consultation, integration assistance, and after-sales technical support from engineers with hands-on coherent test and measurement experience
FAQs
What is the main advantage of the built-in local oscillator in CORX?
The integrated tunable LO eliminates the need for an external tunable laser source — removing the cost, bench space, alignment complexity, and potential phase instability of a separate LO instrument. The CORX’s built-in LO covers the full C-band (190.70–196.65 THz) with a linewidth of 25 kHz typical and ±0.3 GHz frequency accuracy over 24 hours, guaranteeing stable, phase-coherent signal mixing from the moment of power-up without external calibration.
What is the main advantage of the built-in local oscillator in the CORX?
The integrated tunable LO eliminates the need for an external tunable laser source — removing the cost, bench space, alignment complexity, and potential phase instability of a separate LO instrument. The CORX’s built-in LO covers the full C-band (190.70–196.65 THz) with a linewidth of 25 kHz typical and ±0.3 GHz frequency accuracy over 24 hours, guaranteeing stable, phase-coherent signal mixing from the moment of power-up without external calibration.
What bandwidth options are available for the CORX, and which should I choose?
The CORX is available in 20 GHz, 40 GHz, and 60 GHz bandwidth variants, selected at time of order. Choose 20 GHz for 100G coherent systems (DP-QPSK at 28–32 GBaud). Choose 40 GHz for 200G/400G systems (DP-16QAM up to 56 GBaud). Choose 60 GHz for 800G, 1.6T, and next-generation terabit research supporting baud rates beyond 120 GBaud. The bandwidth variant is factory-configured and cannot be changed after order, so select based on your current and near-future requirements.
Can the CORX be used with any real-time oscilloscope?
Yes. The CORX delivers four single-ended RF outputs — XI, XQ, YI, YQ — through 50 Ohm SMA connectors with a 600 mV output swing, making it compatible with any real-time oscilloscope, digitiser, or ADC with standard 50 Ohm SMA inputs. No special adapters, impedance matching networks, or oscilloscope-specific configurations are required. Simply connect the four SMA outputs to four input channels of the oscilloscope and begin capturing IQ waveforms.
What modulation formats does the CORX support?
The CORX supports coherent detection and analysis of all major dual-polarisation coherent modulation formats: DP-QPSK, DP-8PSK, DP-16QAM, DP-64QAM, and higher-order formats. It provides full IQ separation for both X and Y polarisations simultaneously, enabling complete constellation analysis, EVM measurement, phase error characterisation, and BER-related metric extraction for formats used in 100G, 200G, 400G, 800G, and next-generation optical networks.
Is the CORX suitable for production test environments?
The CORX is a fully integrated, turn-key coherent optical receiver instrument that combines a built-in tunable local oscillator, polarisation-diversity optical hybrid, balanced photodetectors, and four TIA-amplified RF outputs in a single 1U chassis. It connects directly to any real-time oscilloscope via four SMA RF outputs and enables precise dual-polarisation IQ detection of C-band optical signals modulated with QPSK, 8-PSK, 16-QAM, 64-QAM, and higher-order coherent formats. It is used for coherent transmitter characterisation, DWDM receiver testing, DSP algorithm development, and optical component qualification.
Can I automate CORX measurements with Python or LabVIEW?
Yes. The CORX supports a full SCPI-compatible command set over both USB and Ethernet, making it directly integrable with Python (PyVISA), LabVIEW (NI-VISA), MATLAB (Instrument Control Toolbox), and any other automation framework supporting SCPI over TCP/IP or USBTMC. This enables programmatic control of LO frequency, optical attenuation, and power settings within automated test sequences for high-throughput production testing or scripted research workflows.
What is the IQ skew specification of the CORX, and why does it matter?
The CORX specifies ±3 ps IQ skew (within a polarisation) and ±5 ps XY polarisation skew (between polarisations). IQ skew is the timing difference between the I and Q channels — even small skew values cause constellation rotation and EVM degradation that are indistinguishable from transmitter impairments if the receiver itself is not characterised. The CORX’s tight skew specification ensures that measurement results accurately reflect the device under test, not the measurement instrument.
What is the wavelength range of the CORX?
The CORX operates over the full C-band: 1528–1568 nm (190.70–196.65 THz), aligned to the ITU-T G.694.1 DWDM frequency grid. The built-in LO is continuously tunable across this entire range in 1 MHz steps, enabling channel-by-channel testing of all standard C-band DWDM channels without a separate LO source. L-band operation is not currently supported.
How does the built-in VOA function in the CORX?
The CORX includes an integrated 10 dB variable optical attenuator (VOA) on the signal input path. The VOA allows engineers to adjust the input signal power level to optimise the operating point of the balanced photodetectors — maximising receiver linearity and avoiding detector saturation. This is particularly important when characterising transmitters operating at varying output power levels or when measuring low-power signals near the receiver sensitivity floor.
Does the CORX require any special software or drivers to operate?
No. The CORX includes a browser-based web GUI accessible from any web-enabled device — PC, tablet, or smartphone — connected via Ethernet. No software downloads, drivers, or plugins are required for manual operation. For SCPI automation, standard VISA drivers (NI-VISA or open-source alternatives) are used over USB or Ethernet — no proprietary software or licensing costs involved.
Who distributes the CORX in India, and what support is provided?
United Spectrum Instruments is the official authorised distributor of the CORX Coherent Optical Receiver in India. We provide complete pre-sales application consultation (bandwidth selection, oscilloscope compatibility, integration planning), after-sales technical support (SCPI automation guidance, calibration, troubleshooting), and GST-compliant, MSME-registered procurement for institutional and government customers.
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FAQs
What is the main advantage of the built-in local oscillator in CORX?
The integrated tunable LO eliminates the need for an external tunable laser source — removing the cost, bench space, alignment complexity, and potential phase instability of a separate LO instrument. The CORX’s built-in LO covers the full C-band (190.70–196.65 THz) with a linewidth of 25 kHz typical and ±0.3 GHz frequency accuracy over 24 hours, guaranteeing stable, phase-coherent signal mixing from the moment of power-up without external calibration.
What is the main advantage of the built-in local oscillator in the CORX?
The integrated tunable LO eliminates the need for an external tunable laser source — removing the cost, bench space, alignment complexity, and potential phase instability of a separate LO instrument. The CORX’s built-in LO covers the full C-band (190.70–196.65 THz) with a linewidth of 25 kHz typical and ±0.3 GHz frequency accuracy over 24 hours, guaranteeing stable, phase-coherent signal mixing from the moment of power-up without external calibration.
What bandwidth options are available for the CORX, and which should I choose?
The CORX is available in 20 GHz, 40 GHz, and 60 GHz bandwidth variants, selected at time of order. Choose 20 GHz for 100G coherent systems (DP-QPSK at 28–32 GBaud). Choose 40 GHz for 200G/400G systems (DP-16QAM up to 56 GBaud). Choose 60 GHz for 800G, 1.6T, and next-generation terabit research supporting baud rates beyond 120 GBaud. The bandwidth variant is factory-configured and cannot be changed after order, so select based on your current and near-future requirements.
Can the CORX be used with any real-time oscilloscope?
Yes. The CORX delivers four single-ended RF outputs — XI, XQ, YI, YQ — through 50 Ohm SMA connectors with a 600 mV output swing, making it compatible with any real-time oscilloscope, digitiser, or ADC with standard 50 Ohm SMA inputs. No special adapters, impedance matching networks, or oscilloscope-specific configurations are required. Simply connect the four SMA outputs to four input channels of the oscilloscope and begin capturing IQ waveforms.
What modulation formats does the CORX support?
The CORX supports coherent detection and analysis of all major dual-polarisation coherent modulation formats: DP-QPSK, DP-8PSK, DP-16QAM, DP-64QAM, and higher-order formats. It provides full IQ separation for both X and Y polarisations simultaneously, enabling complete constellation analysis, EVM measurement, phase error characterisation, and BER-related metric extraction for formats used in 100G, 200G, 400G, 800G, and next-generation optical networks.
Is the CORX suitable for production test environments?
The CORX is a fully integrated, turn-key coherent optical receiver instrument that combines a built-in tunable local oscillator, polarisation-diversity optical hybrid, balanced photodetectors, and four TIA-amplified RF outputs in a single 1U chassis. It connects directly to any real-time oscilloscope via four SMA RF outputs and enables precise dual-polarisation IQ detection of C-band optical signals modulated with QPSK, 8-PSK, 16-QAM, 64-QAM, and higher-order coherent formats. It is used for coherent transmitter characterisation, DWDM receiver testing, DSP algorithm development, and optical component qualification.
Can I automate CORX measurements with Python or LabVIEW?
Yes. The CORX supports a full SCPI-compatible command set over both USB and Ethernet, making it directly integrable with Python (PyVISA), LabVIEW (NI-VISA), MATLAB (Instrument Control Toolbox), and any other automation framework supporting SCPI over TCP/IP or USBTMC. This enables programmatic control of LO frequency, optical attenuation, and power settings within automated test sequences for high-throughput production testing or scripted research workflows.
What is the IQ skew specification of the CORX, and why does it matter?
The CORX specifies ±3 ps IQ skew (within a polarisation) and ±5 ps XY polarisation skew (between polarisations). IQ skew is the timing difference between the I and Q channels — even small skew values cause constellation rotation and EVM degradation that are indistinguishable from transmitter impairments if the receiver itself is not characterised. The CORX’s tight skew specification ensures that measurement results accurately reflect the device under test, not the measurement instrument.
What is the wavelength range of the CORX?
The CORX operates over the full C-band: 1528–1568 nm (190.70–196.65 THz), aligned to the ITU-T G.694.1 DWDM frequency grid. The built-in LO is continuously tunable across this entire range in 1 MHz steps, enabling channel-by-channel testing of all standard C-band DWDM channels without a separate LO source. L-band operation is not currently supported.
How does the built-in VOA function in the CORX?
The CORX includes an integrated 10 dB variable optical attenuator (VOA) on the signal input path. The VOA allows engineers to adjust the input signal power level to optimise the operating point of the balanced photodetectors — maximising receiver linearity and avoiding detector saturation. This is particularly important when characterising transmitters operating at varying output power levels or when measuring low-power signals near the receiver sensitivity floor.
Does the CORX require any special software or drivers to operate?
No. The CORX includes a browser-based web GUI accessible from any web-enabled device — PC, tablet, or smartphone — connected via Ethernet. No software downloads, drivers, or plugins are required for manual operation. For SCPI automation, standard VISA drivers (NI-VISA or open-source alternatives) are used over USB or Ethernet — no proprietary software or licensing costs involved.
Who distributes the CORX in India, and what support is provided?
United Spectrum Instruments is the official authorised distributor of the CORX Coherent Optical Receiver in India. We provide complete pre-sales application consultation (bandwidth selection, oscilloscope compatibility, integration planning), after-sales technical support (SCPI automation guidance, calibration, troubleshooting), and GST-compliant, MSME-registered procurement for institutional and government customers.
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