Optical Modulator Module with Mode Converter for Bias Point Stability
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Solution Overview
Problem
In optical communication systems, the use of space optical systems for combining signal light beams from optical modulators into optical fibers leads to bias point shifts due to interference from higher-order mode light beams, causing signal quality deterioration and alignment issues.
Innovation Solution
An optical element module with an unnecessary light beam removing unit, such as a slab waveguide, is integrated between the output waveguide and radiated light beam waveguide near the substrate end, utilizing the first lens unit to suppress input of higher-order mode and leaked light beams into the optical fiber, and optionally incorporating a light absorbing unit to enhance suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a space optical system is used to combine signal light beams from optical modulators into optical fibers, then the optical element module can achieve wide bandwidth and flexible light beam combination, but higher-order mode light beams are coupled into the optical fiber causing bias point shifts and signal quality deterioration
Solution Approach 1:
The patent extracts and removes higher-order mode light beams from the optical system using a mode converter and selective coupling mechanism. The mode converter transforms higher-order modes into different propagation modes that can be separated from the fundamental mode, allowing only the desired signal light to enter the optical fiber while discarding the harmful higher-order modes.
Solution Approach 2:
The patent introduces a mode converter as an intermediary component between the optical modulator and the optical fiber. This intermediary device mediates the light beam transmission by converting unwanted higher-order modes into separable forms, enabling clean signal transmission without direct coupling of harmful modes into the fiber.
2Measurement precision
If positional relationships between substrate, lens units, and optical components are precisely maintained, then signal quality is preserved, but any slight deviation causes unnecessary light beams to mix into the signal light beam and interfere with signal transmission
Solution Approach 1:
The patent applies beforehand cushioning by pre-converting higher-order mode light beams into separable modes before they can cause interference. The mode converter is positioned upstream to transform problematic modes into different propagation characteristics, creating a buffer that prevents alignment deviations from causing harmful light mixing in the final signal path.
Solution Approach 2:
The patent converts the harmful higher-order mode light beams into beneficial separable modes through the mode converter. By transforming the problematic higher-order modes into distinct propagation modes, the system turns potential interference sources into easily filterable components, improving overall signal quality.
3Object-generated harmful factors
If leaked light beam removing means is disposed on both sides of the output waveguide, then some leaked light is suppressed, but higher-order mode light beams are still coupled into the optical fiber causing bias point shift phenomena
Solution Approach 1:
The patent extracts higher-order mode light beams from the output waveguide using a mode converter that transforms these modes into separable forms. This extraction mechanism specifically targets and removes higher-order modes that cause bias point shifts, complementing the leaked light suppression measures already in place.
Solution Approach 2:
The patent changes the propagation parameters of higher-order mode light beams by using a mode converter to transform them into different modes with distinct propagation characteristics. This parameter change enables selective coupling or filtering, allowing the system to distinguish and separate harmful higher-order modes from the fundamental signal mode.
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 configuration effectively reduces the mixing of unnecessary light beams, thereby minimizing bias point shifts and maintaining signal quality even with positional deviations of optical components.
Implementation Method 1
a first lens unit that is disposed on an end surface of the substrate, and includes a lens portion at which a signal light beam emitted from the optical modulator unit is collimated
Implementation Method 2
a second lens unit that introduces the signal light beam passing through the first lens unit to an optical fiber
Implementation Method 3
An unnecessary light beam removing unit, which suppresses input of a higher-order mode light beam propagating through the output waveguide or a leaked light beam propagating through the inside of the substrate into the optical fiber through the lens portions of the first lens unit, is provided between the output waveguide and the radiated light beam waveguide
Data Source
AI summary
Provided is an optical element module including: a substrate; an optical modulator unit that is formed in the substrate and includes an optical waveguide; a first lens unit that is disposed on an end surface of the substrate, and includes a lens portion at which a signal light beam emitted from the optical modulator unit is collimated; and a second lens unit that introduces the signal light beam passing through the first lens unit to an optical fiber. The optical modulator unit includes a Mach-Zehnder type optical waveguide, a Y-branch coupler of the Mach-Zehnder type optical waveguide includes an output waveguide through which a signal light beam is guided, and a radiated light beam waveguide through which a radiated light beam is guided, and an unnecessary light beam removing unit, which suppresses input of a higher-order mode light beam propagating through the output waveguide or a leaked light beam propagating through the inside of the substrate into the optical fiber through the lens portions of the first lens unit, is provided between the output waveguide and the radiated light beam waveguide in the vicinity of an end of the substrate.