Coherent Wavelength Locking via Dithering Sequence
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Coherent optical communication systems face challenges in maintaining frequency stability of lasers due to variations caused by temperature and output power, leading to initial Carrier Frequency Offset (CFO) values that often exceed the capture range of conventional CFO loops, necessitating expensive wavelength lockers.
Innovation Solution
An optical communication device with a device controller that applies a series of frequency hops, known as a dithering sequence, to the laser to bring the initial CFO within the capture range, allowing for reliable frequency locking without the need for expensive wavelength lockers, using a Digital Signal Processor (DSP) and a controller to manage the Thermo-Electric Cooler (TEC) for precise frequency adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional CFO loop is used for frequency locking, then the system structure is simple, but the initial Carrier Frequency Offset (CFO) often exceeds the capture range, preventing reliable frequency locking
Solution Approach 1:
The patent applies preliminary action by implementing a dithering sequence that pre-adjusts the laser frequency before the CFO loop operates. The dithering sequence generates a series of frequency hops to bring the initial CFO within the capture range of the CFO loop, enabling reliable frequency locking without requiring complex additional hardware.
2Stability of the object's composition
If an optical wavelength locker is used to improve laser frequency stability, then the frequency stability improves, but the device cost and complexity increase
Solution Approach 1:
The patent implements self-service by enabling the laser frequency control system to adjust itself using the dithering sequence and CFO loop. The system uses the received optical signal and local oscillator to generate feedback that automatically drives the frequency hops and CFO correction, eliminating the need for external wavelength lockers or complex frequency stabilization equipment.
3Reliability
If the CFO loop operates continuously with tight locking, then the reception quality improves, but the power consumption increases
Solution Approach 1:
The patent applies periodic action by implementing the dithering sequence as a series of discrete frequency hops rather than continuous adjustment. The CFO loop operates periodically to correct frequency offsets, and the system can relax the locking tightness when reception quality is sufficient, reducing power consumption while maintaining acceptable performance.
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 enables cost-effective wavelength locking, suitable for short-haul networking and other applications, by simplifying laser requirements and reducing power consumption while maintaining high reception quality and minimizing error rates.
Implementation Method 1
the device controller is configured to adjust the frequency of the laser, and to apply the series of frequency hops to the frequency of the laser, by controlling a Thermo-Electric Cooler (TEC) coupled to the laser
Data Source
AI summary
An optical communication device includes a laser, a transmitter (Tx), a receiver (Rx) and a device controller. The laser is configured to generate an optical carrier. The transmitter is configured to generate an optical Tx signal using the optical carrier and to transmit the optical Tx signal to a peer optical communication device. The receiver is configured to receive an optical Rx signal from the peer optical communication device, and to down-convert the optical Rx signal using the optical carrier. The device controller is configured to adjust a frequency of the laser to reduce a Carrier Frequency Offset (CFO) between the received optical Rx signal and the optical carrier generated by the laser, including conditionally applying to a frequency of the laser a series of frequency hops in accordance with a defined dithering sequence.