Silicon Wavelength Locker Layout for Low-Loss C+L Band Locking
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Solution Overview
Problem
The 4x4 MMI couplers in wavelength division multiplexing systems suffer from limited bandwidth, leading to high insertion loss in C+L band applications, reducing optical power availability for data signals and degrading signal quality.
Innovation Solution
An integrated wavelength locker is designed with two Mach-Zehnder interferometers on a silicon substrate, featuring waveguides of differing lengths to control the delta peak during fabrication, eliminating the need for tuning elements and minimizing variance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a 4x4 MMI coupler is used in a wavelength locker, then the device provides a well-defined phase difference between outputs that can be used as a reference signal, but the insertion loss increases significantly as the operational wavelength deviates from the central wavelength, limiting the bandwidth to C-band applications only
Solution Approach 1:
The patent divides the single 4x4 MMI coupler into multiple separate MMI couplers (at least two), each optimized for specific wavelength ranges. This segmentation allows each coupler to maintain low insertion loss at its designated wavelengths while collectively covering the broader C+L band spectrum.
Solution Approach 2:
The patent extends the wavelength coverage by adding spectral dimension coverage through multiple couplers with different central wavelengths. Instead of relying on a single coupler's limited spectral response, the system uses multiple couplers whose combined spectral responses cover the entire C+L band.
2Adaptability or versatility
If the operational wavelength is extended to C+L band applications, then the bandwidth is increased, but the insertion loss becomes quite high at wavelengths farther from the central wavelength, reducing optical power availability for data signals
Solution Approach 1:
The patent segments the wavelength coverage responsibility among multiple MMI couplers, with each coupler optimized for a specific wavelength range within the C+L band. This allows the system to achieve broad wavelength coverage while maintaining low insertion loss across the entire band.
Solution Approach 2:
The patent creates a multi-functional wavelength locker system where each MMI coupler serves a specific wavelength range function, and collectively they provide universal coverage across the entire C+L band. The system can handle multiple wavelength ranges simultaneously with optimized performance for each.
3Reliability
If more optical power is sent to the wavelength locker to compensate for high insertion loss, then the wavelength locking function is maintained, but less optical power is available for the data signal, leading to reduced efficiency and signal degradation
Solution Approach 1:
By segmenting the wavelength locking function across multiple couplers with lower individual insertion losses, the system maintains reliable wavelength locking without requiring excessive optical power, thereby preserving more power for data transmission.
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 provides lower insertion loss across a wide bandwidth, enabling flexible wavelength peak selection and enhancing the efficiency and reliability of optical communication systems.
Implementation Method 1
a first Mach-Zehnder interferometer and a second Mach-Zehnder interferometer, wherein the first Mach-Zehnder interferometer and the second Mach-Zehnder interferometer each comprises an input coupler comprising multiple outputs, an output coupler comprising multiple inputs, a first waveguide formed on the silicon substrate and extending between a first output of the input coupler and a first input of the output coupler
Implementation Method 2
a first waveguide formed on the silicon substrate and extending between a first output of the input coupler and a first input of the output coupler, and a second waveguide formed on the silicon substrate and extending between a second output of the input coupler and a second input of the output coupler
Data Source
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AI summary
In some examples, an integrated wavelength locker fabricated on a silicon substrate comprises a first Mach-Zehnder interferometer and a second Mach-Zehnder interferometer, wherein the first Mach-Zehnder interferometer and the second Mach-Zehnder interferometer each comprises an input coupler comprising multiple outputs, an output coupler comprising multiple inputs, a first waveguide formed on the silicon substrate and extending between a first output of the input coupler and a first input of the output coupler, and a second waveguide formed on the silicon substrate and extending between a second output of the input coupler and a second input of the output coupler, wherein the first waveguide is associated with a first length, wherein the second waveguide is associated with a second length, wherein the first length is different from the second length, wherein a difference between the first length and the second length defines a delay length of the first Mach-Zehnder interferometer and the second Mach-Zehnder interferometer, respectively, wherein the first length and/or the second length differs between the first Mach-Zehnder interferometer and the second Mach-Zehnder interferometer.