Coherent Receiver LO Wavelength Alignment for Uncalibrated Lasers
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Solution Overview
Problem
Existing communication systems face challenges in implementing wavelength alignment for uncalibrated lasers in optical networks, with a focus on wavelength alignment for uncalibrated lasers in optical networks, specifically in passive optical networks (PONs), which are cost-sensitive and require low-cost components.
Innovation Solution
An apparatus and method for adjusting the operation parameter of a laser, such as temperature or bias current, to align the emission frequency of a local oscillator in a coherent optical receiver, using electrical power indications to determine a target range for wavelength alignment, enabling the use of uncalibrated lasers in PONs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uncalibrated low-cost lasers are used in coherent receivers, then cost is reduced, but wavelength alignment precision deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the coherent receiver measures the wavelength of downstream signals and feeds this information back to adjust the local oscillator laser's wavelength. This closed-loop control enables uncalibrated low-cost lasers to achieve accurate wavelength alignment by continuously monitoring and correcting wavelength deviations based on measured feedback from the optical network.
Solution Approach 2:
The patent changes the operating parameters of the local oscillator laser (such as temperature, current, or voltage) to adjust its emission wavelength. By dynamically modifying these parameters based on feedback measurements, the system achieves wavelength alignment without requiring pre-calibrated expensive lasers, thus resolving the contradiction between cost and precision.
2Device complexity
If uncalibrated lasers are used without wavelength alignment, then device complexity is reduced, but communication reliability deteriorates
Solution Approach 1:
The system employs feedback control where the coherent receiver measures downstream signal wavelengths and adjusts the local oscillator accordingly. This feedback mechanism ensures reliable communication by automatically compensating for wavelength mismatches while keeping the device configuration relatively simple, avoiding the need for complex pre-calibration procedures.
Solution Approach 2:
The coherent receiver performs self-alignment by measuring the wavelength of downstream signals and automatically adjusting its local oscillator laser without external intervention. This self-service capability ensures communication reliability while minimizing device complexity, as the system configures itself during operation rather than requiring complex external calibration equipment.
3Measurement precision
If full calibration and testing of laser chips are performed, then wavelength alignment precision is improved, but manufacturing cost increases
Solution Approach 1:
Instead of performing comprehensive calibration during manufacturing, the patent implements preliminary wavelength measurement and alignment action during system operation. The coherent receiver measures the wavelength of downstream signals and adjusts the local oscillator accordingly, achieving the necessary precision without requiring expensive pre-calibration of each laser chip.
Solution Approach 2:
The system uses feedback control to achieve wavelength alignment precision that would otherwise require expensive pre-calibration. By measuring the actual wavelength of downstream signals and adjusting the local oscillator based on this feedback, the system achieves high precision while using inexpensive uncalibrated laser chips, thereby reducing manufacturing costs.
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 efficient wavelength alignment of low-cost, uncalibrated lasers in PONs, reducing the cost of coherent receivers by allowing coarse alignment within a short time, and maintaining alignment even when wavelength drift occurs.
Implementation Method 1
The coherent receiver mixes the received signal with a local reference laser, also known as local oscillator (LO), which allows to detect the phase, amplitude, and polarization modulation
Implementation Method 2
adjusting an operation parameter of a laser, thereby adjusting an emission frequency of the laser
Data Source
Figure 1a~1b
Figure 2a~3
Figure 4
AI summary
The present invention discloses an apparatus comprising means for: adjusting an operation parameter of a laser (210), thereby adjusting an emission frequency of the laser (210), wherein the laser (210) is suitable to be used as a local oscillator for a coherent optical receiver in an optical network unit, ONU, wherein the laser (210) is uncalibrated in terms of the relationship between the operation parameter and the emission frequency of the laser; obtaining an indication of an electrical power of a downstream signal received by the coherent optical receiver, while adjusting the operation parameter; determining a first target range of the operation parameter based on a relationship between the obtained indication of the electrical power and the corresponding operation parameter, wherein the emission frequency of the laser corresponding to the first target range is aligned to the frequency of the downstream signal.