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Polarization-insensitive local-oscillator-carrier loopback modulation for a cost-effective and high-port-count
Optics Letters
|August 1, 2022
Summary
A novel polarization-alignment circuit stabilizes optical switches by ensuring consistent light polarization, enabling larger systems. This breakthrough supports high-port-count optical switches using loopback modulation without tunable lasers.
Area of Science:
- Optical Engineering
- Telecommunications
- Photonics
Background:
- Wavelength-routing optical switches typically require tunable lasers at each input port.
- Coherent transmission offers an alternative using loopback modulation but suffers from instability due to polarization rotation.
Purpose of the Study:
- To develop a stable and effective method for loopback modulation in optical switches.
- To enable high-port-count optical switch systems by overcoming polarization-related instability.
Main Methods:
- Proposed a simple polarization-alignment circuit using passive components.
- Aligned the local oscillator (LO) carrier's polarization to the x-direction of a dual-polarization (DP) IQ modulator.
- Verified the circuit's effectiveness in a large-scale optical switch system experiment.
Main Results:
- Achieved stable modulation with Q-variation below 0.8 dB, irrespective of fiber birefringence.
- Demonstrated a 1,856 × 1,856 optical switch scale using the proposed circuit and loopback modulation.
- Eliminated the need for wavelength-tunable lasers in the optical switch system.
Conclusions:
- The proposed polarization-alignment circuit effectively stabilizes loopback modulation for optical switches.
- This passive circuit enables the construction of large-scale, high-port-count optical switching systems.
- The solution offers a practical and stable approach for advanced optical communication networks.
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