Optical Loopback Bandwidth Adaptation in Pre-Occupied Spectrum
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Solution Overview
Problem
Existing photonic loopback techniques in optical networking systems face challenges when performing tests in pre-occupied spectrum, as they require dedicated free spectral locations which are often unavailable due to pre-provisioned Media Channels, limiting the ability to perform loopback tests without impacting in-service traffic.
Innovation Solution
The system automatically adjusts bandwidth by either reducing the modem's baud rate or adding additional deadbands outside the loopback channel to ensure sufficient spectral width for loopback tests, avoiding filter-roll off penalties and preserving in-service traffic integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If photonic loopback tests are performed in pre-occupied spectrum, then the ability to test modem functionality is improved, but filter-roll off penalties and interference with neighboring channels occur due to insufficient spectral width
Solution Approach 1:
The system dynamically adjusts the bandwidth allocation for loopback tests based on the presence and status of neighboring channels. When neighboring channels are detected, the system automatically reduces the loopback bandwidth to prevent interference. This dynamic adaptation allows the system to perform loopback tests in pre-occupied spectrum while maintaining signal integrity by adjusting spectral width in real-time according to channel conditions.
Solution Approach 2:
The system changes the baud rate parameter of the modem based on the available spectral width. When bandwidth is reduced to accommodate pre-provisioned Media Channels, the system automatically lowers the baud rate to match the reduced spectral allocation. This parameter adjustment ensures that loopback tests can proceed without filter-roll off penalties while maintaining adequate signal quality for validation.
2Measurement precision
If dedicated free spectral locations are allocated for loopback tests, then test accuracy is improved, but spectrum availability is reduced due to pre-provisioned Media Channels
Solution Approach 1:
The system applies different quality requirements to different spectral regions. Instead of requiring uniform high-quality dedicated spectrum throughout, the system identifies specific local regions within the pre-provisioned Media Channels that are suitable for loopback testing. By selecting optimal local locations and adjusting bandwidth dynamically, the system achieves adequate test accuracy without requiring extensive dedicated free spectrum, thus utilizing the pre-occupied spectrum more efficiently.
3Reliability
If bandwidth is reduced for loopback tests to preserve in-service traffic, then neighboring channel integrity is improved, but loopback test capability is degraded
Solution Approach 1:
The system employs feedback mechanisms to monitor the effects of bandwidth reduction on loopback test performance. By continuously assessing signal quality and test results, the system can determine whether the reduced bandwidth is sufficient for valid testing. This feedback loop allows operators to verify that in-service traffic integrity is maintained while confirming that loopback tests remain effective, enabling informed decisions about bandwidth allocation for testing purposes.
Data Source
AI summary
A system and method are provided for performing a loopback test in a pre-provisioned multi-channel optical network. A controller determines actual spectral availability within an optical spectrum, irrespective of reserved or pre-planned channel allocations, and overrides spectrum reservation limits to define an effective loopback-test bandwidth. The controller configures a selected network-management channel (NMC) and associated modem for the loopback test based on the determined availability, enabling loopback operation even within an occupied or partially utilized spectrum. The system dynamically adjusts modem transmission parameters and establishes spectral guard bands or deadbands as needed to preserve integrity of in-service traffic and mitigate filter roll-off effects. The approach allows flexible, non-disruptive photonic loopback testing in deployed Reconfigurable Optical Add/Drop Multiplexers (ROADMs) or other multi-channel optical environments without re-provisioning the existing channel plan.