Optical Receptacle NA Control for Signal Stability
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Solution Overview
Problem
Conventional optical signal transmission systems face challenges in maintaining a stable optical line while achieving high frequency response speed and reliability, due to excessive numerical aperture (NA) of the light beam incident on the light receiving element, which leads to aberration and reduced focusing properties, and is exacerbated by surface reflectance issues.
Innovation Solution
The system employs a configuration where the receiving fiber has a larger core diameter than the transmitting fiber, with a solid immersion lens coupled to the light receiving element, and a lens arrangement that reduces the NA of the signal light incident on the receiving fiber, while using anti-reflective coatings to minimize surface reflection effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the receiving fiber has a smaller core diameter to match the light receiving element size, then the frequency response speed is improved, but the optical coupling efficiency deteriorates due to excessive NA
Solution Approach 1:
The patent changes the NA parameter of the receiving fiber to be smaller than that of the transmitting fiber. This parameter change allows the light beam to be properly coupled into the light receiving element without excessive NA, thereby maintaining both high frequency response speed and good optical coupling efficiency. The receiving fiber is designed with NA2ex < NApd (NA of light incident on light receiving element), which resolves the contradiction between small core diameter requirements for speed and NA matching for efficiency.
2Reliability
If the NA of the light beam incident on the light receiving element is increased to improve coupling, then the focusing properties deteriorate due to aberration
Solution Approach 1:
The patent controls the NA parameter of the light beam incident on the light receiving element by designing the receiving fiber with a smaller NA than the transmitting fiber. This ensures that NApd (NA of light incident on light receiving element) remains within an optimal range that prevents excessive aberration while maintaining good coupling efficiency. The relationship NA2ex < NApd < 0.5 is established to balance coupling efficiency and focusing properties.
3Reliability
If the receiving fiber core diameter is reduced to match the transmitting fiber, then the etendue matching is improved, but the tolerance for alignment error deteriorates
Solution Approach 1:
The patent changes the core diameter and NA parameters of the receiving fiber to be different from the transmitting fiber. Specifically, the receiving fiber has a larger core diameter (φ2ex > φ1ex) and smaller NA (NA2ex < NA1ex) than the transmitting fiber. This parameter change maintains etendue matching (φ2ex×NA2ex ≥ φ1ex×NA1ex) while providing larger alignment tolerance due to the larger receiving fiber core diameter.
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 stabilizes the optical line, maintains high frequency response speed, and improves system reliability by reducing aberration and surface reflection, allowing for efficient signal transmission without excessive optical loss.
Implementation Method 1
an optical connector disposed between the transmitting fiber and the receiving fiber and comprising a lens configured to guide the signal light emitted from the exit face of the transmitting fiber to the entrance face of the receiving fiber
Implementation Method 2
the light receiving element comprising a receiving surface on which the signal light transmitted through the receiving fiber is incident and being configured to subject the incident signal light to photoelectric conversion
Implementation Method 3
the lens of the optical receptacle being configured to guide the signal light transmitted through the receiving fiber to the receiving surface
Data Source
AI summary
In an optical signal transmission system for transmitting signal light through a transmitting fiber, an optical connector, and a receiving fiber to an optical receptacle, the relationships ϕ1ex<ϕ2en and ϕpd<ϕ2en are satisfied, where ϕ1ex is the core diameter of the transmitting fiber at the exit face of the transmitting fiber, ϕ2en is the core diameter of the receiving fiber at the entrance face of the receiving fiber, and ϕpd is the diameter of a receiving surface of a light receiving element in the optical receptacle, and the relationship NA1ex>Na2en is satisfied, where, in the optical connector, NA1ex is the numerical aperture (NA) of the signal light emitted from the transmitting fiber, and NA2en is the NA of the signal light incident on the receiving fiber.