Broadband Optical Isolator Using N-Arm Interferometer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing integrated optical isolators face challenges such as high losses, low isolation characteristics, and narrow bandwidth due to their design, particularly when monolithically integrating lasers and optical amplifiers with other components, and current electro-optic methods like traveling-wave modulators are either long or difficult to design effectively.
Innovation Solution
An integrated broadband optical isolator is developed using an N-arm interferometer with pairs of sinusoidally driven phase modulators, where each pair acts as a narrow-band isolator, achieving broadband isolation by appropriately phasing the drives and ensuring equal optical path lengths, resulting in minimal intrinsic loss and no residual frequency shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional integrated optical isolators are used, then isolation function is provided, but bandwidth is narrow and losses are high
Solution Approach 1:
The optical isolator is divided into N independent arms (where N>2), each arm containing its own phase modulators and optical path. By segmenting the isolation function across multiple arms with different optical path lengths, the system achieves broadband operation while maintaining low losses in each individual arm, resolving the contradiction between narrow bandwidth and high optical loss.
Solution Approach 2:
The patent transitions from a single-path isolator to a multi-dimensional N-arm interferometer structure. By introducing multiple spatial dimensions (arms) with different optical path lengths, the system expands the operational bandwidth without proportionally increasing losses, as each arm contributes to the overall isolation across different frequency ranges.
2Reliability
If traditional electro-optic methods like traveling-wave modulators are used, then isolation is achieved, but device length becomes very long
Solution Approach 1:
The isolation function is segmented into N discrete arms, each with compact phase modulator pairs. This segmentation allows the total isolation function to be distributed across shorter individual paths, reducing the overall device length compared to traditional traveling-wave modulators while maintaining reliable isolation characteristics through the combined effect of all arms.
Solution Approach 2:
Multiple short optical paths in N arms are merged into a unified interferometer structure. By combining the isolation effects of N separate phase modulator pairs with different optical path lengths, the system achieves the same reliability as long traveling-wave modulators but with a significantly reduced overall device length.
3Adaptability or versatility
If multiple phase modulators are used in each arm, then broadband isolation is achieved, but device complexity increases
Solution Approach 1:
Each arm in the N-arm interferometer serves multiple functions: it provides isolation for specific frequency ranges, contributes to broadband operation when combined with other arms, and maintains a standardized structure with phase modulators. This multi-functionality reduces overall device complexity by using identical building blocks for different purposes across the bandwidth spectrum.
Solution Approach 2:
The system achieves broadband isolation by changing the optical path length parameter across different arms rather than changing the fundamental structure of each arm. By varying only the optical path length parameter while keeping the phase modulator configuration consistent across all N arms, the patent simplifies the overall device design while still achieving broadband operation.
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 substantial broadband isolation with minimal intrinsic loss and no residual frequency shift, allowing for efficient isolation of forward and backward signals, especially when N=4, achieving approximately 20 dB of isolation even with wide bandwidth inputs, and can be implemented in silicon photonics with reduced drive complexity.
Implementation Method 1
sinusoidally driven phase modulators inside an interferometer
Implementation Method 2
N optical waveguides optically connecting the 1×N input optical coupler to the N×1 output optical coupler
Implementation Method 3
1×N input optical coupler, where N>2; a N×1 output optical coupler
Data Source
AI summary
An integrated broadband optical isolator that operates over a wide bandwidth, wherein the optical isolator comprises sinusoidally driven phase modulators inside an interferometer. In one exemplary embodiment the optical isolator comprises: a 1×N input optical coupler, where N>2; a N×1 output optical coupler; N optical waveguides optically connecting the 1×N input optical coupler to the N×1 output optical coupler, each one of the N optical waveguides including two phase modulators, wherein each of the phase modulators are driven at a frequency f and wherein the time it takes an optical signal to travel from the center of one phase modulator in a particular waveguide to the center of the other phase modulator in that particular waveguide is substantially equal to 1/4f.