Sampling Pre-Distortion Unit for Laser Signal Chirp Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional digital transmission systems suffer from nonlinear distortion due to chirping laser signals and chromatic dispersion in fiber optic cables, leading to inter-symbol interference, limited distance, current drive, and bandwidth constraints.
Innovation Solution
A sampling pre-distortion unit is introduced to detect the amplitude of input laser signals, assign symbols based on amplitude, and adjust delay values to counteract distortion, using a shift register and clock to generate pre-distortion signals that compensate for delays caused by chirp and chromatic dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a chirping laser signal is transmitted through a fiber optic cable with chromatic dispersion, then data transmission can be achieved, but nonlinear distortion and inter-symbol interference occur
Solution Approach 1:
The patent applies preliminary anti-action by introducing a pre-distortion signal that is the inverse of the expected nonlinear distortion. The pre-distorter modifies the transmitted signal before it enters the fiber optic cable, pre-compensating for the chromatic dispersion and chirp effects that will occur during transmission. This allows the signal to arrive at the receiver with reduced distortion and inter-symbol interference.
Solution Approach 2:
The patent implements preliminary action by measuring the nonlinear distortion characteristics of the transmission channel in advance and using this information to generate appropriate pre-distortion signals. The system characterizes the channel's chromatic dispersion and laser chirp properties beforehand, then uses this knowledge to pre-compensate future transmissions, improving signal integrity before the distortion occurs.
2Length of stationary object
If transmission distance is increased, then more data can be transmitted, but nonlinear distortion and inter-symbol interference worsen
Solution Approach 1:
The pre-distorter applies preliminary anti-action by calculating the expected distortion based on transmission distance and fiber characteristics, then pre-compensating the signal accordingly. The system adjusts the pre-distortion parameters based on the anticipated transmission distance, allowing signals to be transmitted over longer distances while maintaining signal quality by counteracting the cumulative chromatic dispersion effects before they degrade the signal.
3Power
If laser current drive is increased, then transmission power is improved, but chirp-induced distortion increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the pre-distortion parameters based on the laser operating conditions and measured channel characteristics. The system modifies the pre-distortion signal parameters to compensate for chirp effects that vary with laser current drive, allowing the transmission power to be increased while maintaining signal integrity through adaptive parameter adjustment.
4Speed
If bandwidth is increased, then data rate is improved, but nonlinear distortion effects are amplified
Solution Approach 1:
The pre-distorter applies preliminary anti-action by pre-compensating for chromatic dispersion effects that affect different frequency components of the signal. When bandwidth is increased to achieve higher data rates, the pre-distortion technique counteracts the differential group delay across the expanded frequency spectrum, preventing the amplification of nonlinear distortion effects and maintaining signal integrity at higher data rates.
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
The solution effectively mitigates nonlinear distortion, restoring the original signal waveform by dynamically adjusting delay values based on amplitude, thereby enhancing transmission distance, current drive, and bandwidth capabilities.
Implementation Method 1
chromatic dispersion in fiber optic cables
Implementation Method 2
A chirp refers to a change of the wavelength of a laser, typically caused by laser instability
Data Source
AI summary
An optical signal receiver includes a processor, a memory, an input, an output, and a sampling unit in operable communication with the processor and the memory. The sampling unit includes a shift register and a clock, and is configured to receive a laser signal at the input, collect a first sample of the received input laser signal at a first time interval, determine an amplitude of the first sample, assign a first symbol of a plurality of symbols to the determined amplitude, insert the first symbol at a first insertion point within the shift register, and generate a delay value at the output based on a position of the first insertion point with respect to the output.