Coherent Optical Modem ICR Interrupt Path for Fast LOS Detection
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Solution Overview
Problem
Conventional coherent optical modems struggle to achieve fast Loss of Signal (LOS) detection within 1 ms due to reliance on processing circuitry, such as DSP, which requires ADC conversion and SPI bus communication, making it slower than necessary for network protection switching applications.
Innovation Solution
Implement a parallel detection path in the Intradyne Coherent Receiver (ICR) that raises an interrupt to processing circuitry for rapid LOS detection, bypassing ADC conversion and SPI bus communication, utilizing input power reporting circuitry with current mirrors, transimpedance amplifiers, and comparators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional coherent modem detection path (after ADC and SPI bus communication) is used, then processing accuracy is maintained, but LOS detection time exceeds 1 ms
Solution Approach 1:
The detection path is segmented into two parallel paths: a fast detection path that bypasses ADC and SPI bus for rapid LOS detection, and a main detection path that maintains processing accuracy. This segmentation allows the system to achieve fast LOS detection within 1 ms while preserving accurate signal processing capabilities.
Solution Approach 2:
An intermediary fast detection path is introduced between the optical signal input and the main DSP processing path. This intermediary path provides rapid LOS detection capability without interfering with the main processing accuracy, acting as a mediator that resolves the conflict between speed and precision.
2Speed
If ADC conversion and SPI bus communication are used for LOS detection, then accurate signal processing is achieved, but detection speed is insufficient for network protection switching
Solution Approach 1:
The fast detection path performs preliminary LOS detection before the main processing path. By detecting LOS conditions in advance through the fast path, the system can trigger network protection switching immediately without waiting for the slower ADC and SPI bus processes, thereby improving both detection speed and switching reliability.
Solution Approach 2:
The system dynamically switches between detection paths based on conditions. The fast detection path is activated for rapid LOS detection when speed is critical, while the main processing path handles detailed signal analysis. This dynamic approach optimizes both detection speed and reliability for network protection applications.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables sub-1 ms fast LOS detection in coherent modems, comparable to Intensity Modulation with Direct Detection (IMDD) approaches, ensuring rapid network protection switching.
Implementation Method 1
a photodetector configured to convert the received optical signal to a current
Implementation Method 2
a transimpedance amplifier configured to amplify the current
Data Source
AI summary
A coherent optical modem is configured to support fast Loss of Signal (LOS) detection, e.g., <1 ms, and includes an Intradyne Coherent Receiver (ICR) with input power reporting circuitry configured to monitor one or more received optical signals; and processing circuitry communicatively coupled to the ICR and configured to receive a first interrupt from the input power reporting circuitry based on the input power reporting circuitry monitoring the one or more received optical signals, responsive to the first interrupt, prioritize detection of LOS in the processing circuitry, and, responsive to the detection of the LOS, provide a second interrupt to a host device associated with the coherent optical modem.