Optical Coherent Receiver Frequency Response Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The frequency response evaluation of optical coherent receivers is challenging due to the difficulty in controlling and adjusting the phase difference between signal and local light, which can reach the upper or lower limits of the driving signal, making it hard to control the phase difference effectively.
Innovation Solution
The method involves using an optical length adjustor and an optical phase adjustor to equalize the electrical lengths of the optical paths for signal and local light, and adjusting the bias supplied to the phase adjustor to maximize the output of the coherent receiver, with features including decreasing or increasing the bias by 2Vπ when it reaches specific thresholds, and implementing feedback control to stabilize the phase delay/lead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is used to adjust phase difference between signal light and local light, then frequency response evaluation capability is improved, but the driving signal reaches upper or lower limits making phase control impossible
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the optical path length difference between signal light and local light before feedback control is initiated. This initial adjustment ensures that the phase difference operates within the controllable range of the driving signal, preventing the feedback loop from immediately hitting saturation limits and enabling effective frequency response measurement.
2Adaptability or versatility
If optical path length difference exists between signal light and local light, then phase adjustment range is improved, but electrical length equalization becomes difficult
Solution Approach 1:
The patent employs parameter changes by dynamically adjusting the bias voltage applied to the optical phase adjustor to compensate for optical path length differences. By changing the electrical parameter (bias voltage) in response to optical path variations, the system maintains equalized electrical lengths while preserving the necessary phase adjustment range for different measurement conditions.
3Measurement precision
If bias is continuously adjusted by feedback to maximize output, then measurement accuracy is improved, but bias saturation occurs preventing further control
Solution Approach 1:
The patent prevents bias saturation by preliminarily setting the optical path length difference within an optimal range before feedback control begins. This initial configuration ensures that the bias voltage remains within the linear control range of the phase adjustor throughout the measurement process, maintaining both measurement accuracy and control reliability without hitting saturation limits.
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 approach allows for precise evaluation and stabilization of the frequency response of the coherent receiver, preventing saturation of the bias source and ensuring accurate phase control, thereby enabling effective measurement of the frequency response even when the bias exceeds critical levels.
Implementation Method 1
an optical phase adjustor in a second optical path from the optical source to the optical coherent receiver, where the second optical path is provided for the local light, and the optical phase adjustor varies a phase of the local light by suppling a bias thereto
Implementation Method 2
A coherent receiver implemented within the optical coherent system extracts an optical signal by interfering signal light with local light with an optical 90° hybrid device
Implementation Method 3
converts thus extracted optical signal into an electrical signal with a photo-detector
Data Source
AI summary
A technique for measuring an optical coherent receiver is disclosed, where the optical coherent receiver recovers a data by an interference between signal light and local light. The technique includes steps of (i) equalizing optical lengths of the signal light and the local light from the optical source, respectively, and (ii) during a scan of the frequency, maximizing an output of the optical coherent receiver by the feedback control from an output of the optical coherent receive to the phase of the local light. The technique has a feature that, when the feedback control set a delay/lead in the phase of the local light to be 2Vπ−Δ, the delay/lead of the phase of the local light is decreased/increased by 2Vπ, where 2Vπ corresponds to one period of the wavelength of the local light.