Monitoring Multiplexed Laser Array Channels via Optical Tap
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Solution Overview
Problem
Monitoring individual channels in a multiplexed laser array at the output of an optical multiplexer is challenging due to limited space and the inability of directly coupled photodetectors to accurately monitor wavelength in multiplexed laser arrays.
Innovation Solution
A monitoring system is optically coupled to the output of the optical multiplexer, using an optical tap to extract a portion of the multiplexed signal, which includes a monitoring signal generator to provide a monitoring signal that is separated from data signals, allowing for the detection and measurement of power levels without direct coupling to each laser, enabling wavelength locking and confirmation of proper operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photodetectors are directly coupled to each laser in a multiplexed laser array, then laser power and wavelength can be monitored, but the limited space within the multi-channel TOSA makes it infeasible to couple multiple photodetectors to multiple lasers
Solution Approach 1:
The patent combines multiple laser monitoring functions into a single photodetector by using an optical multiplexer to combine the optical signals from multiple lasers into one monitoring path. This allows one photodetector to monitor multiple laser channels simultaneously, resolving the space constraint while maintaining monitoring capability
Solution Approach 2:
The patent introduces an optical multiplexer as an intermediary device between the multiple lasers and the single photodetector. The multiplexer acts as a mediator that separates and directs individual laser wavelengths to the photodetector for monitoring, enabling indirect monitoring without direct coupling to each laser
2Measurement precision
If photodetectors are directly coupled to multiplexed lasers, then monitoring can be performed, but the photodetectors cannot accurately monitor the wavelength of the light after passing through the optical multiplexer
Solution Approach 1:
Instead of monitoring lasers before they enter the multiplexer (where wavelength information is directly available), the patent monitors lasers after they pass through the multiplexer. This inverted approach uses the multiplexer's output characteristics to infer individual laser wavelengths, achieving accurate wavelength monitoring despite the multiplexing process
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
This method allows for effective monitoring of each channel in the multiplexed laser array without the need for multiple photodetectors, ensuring accurate wavelength tuning and operation, thereby enhancing the reliability of optical communication systems.
Implementation Method 1
A monitoring system is optically coupled to the output of the optical multiplexer
Implementation Method 2
A photodetector may be used to monitor the monitoring signal
Data Source
AI summary
Individual channels of a multiplexed laser array in a multi-channel optical transmitter are monitored at an output of an optical multiplexer. The monitoring may be used to confirm proper operation of each of the channels in the multiplexed laser array and/or to perform wavelength locking on each of the channels. Monitoring at the output of the optical multiplexer avoids the use of multiple photodetectors coupled directly to multiple lasers in the multiplexed laser array. The multiplexed laser array generally includes a plurality of laser emitters optically coupled to an optical multiplexer such as an arrayed waveguide grating (AWG). An optical transmitter with a monitored multiplexed laser array may be used, for example, in an optical line terminal (OLT) in a wavelength division multiplexed (WDM) passive optical network (PON) or in any other type of WDM optical communication system capable of transmitting optical signals on multiple channel wavelengths.