Variable Optical Attenuator Lens Gap Design for PDL Reduction
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Solution Overview
Problem
Conventional variable optical attenuators face limitations due to polarization-dependent loss (PDL) and wavelength-dependent loss (WDL), which are exacerbated by assembly stress and material tolerance, leading to inconsistent performance.
Innovation Solution
The design minimizes PDL by ensuring the lens does not contact the cap laterally, reducing radial stress, and compensates WDL by adjusting the tilt angle of the pigtail to optimize wavelength attenuation, thereby reducing material-induced variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the lens is fixed to the cap with lateral contact, then the structural stability is improved, but the radial stress causes polarization-dependent loss (PDL)
Solution Approach 1:
The patent extracts the harmful lateral contact between the lens and cap, creating a gap between them. The lens is held in position by a lens holder rather than direct contact with the cap, eliminating the source of radial stress that causes PDL while maintaining structural stability through the holder mechanism.
Solution Approach 2:
The patent introduces a lens holder as an intermediary component between the lens and the cap. This mediator supports the lens without creating lateral contact stress, thereby preventing PDL generation while still providing the necessary structural support and positioning.
2Manufacturing precision
If the assembly stress is increased to secure components, then the manufacturing precision is improved, but the PDL and WDL variations worsen
Solution Approach 1:
The patent removes the source of stress-induced PDL and WDL variations by eliminating lateral contact between the lens and cap. The gap design ensures that assembly stress does not translate into radial stress on the lens, maintaining precision without harmful side effects.
Solution Approach 2:
The patent changes the physical parameter of the lens-cap interface from direct contact to separated by a gap. This parameter change fundamentally alters the stress transmission characteristics, allowing assembly to be secured without inducing the radial stress that causes PDL and WDL variations.
3Loss of energy
If the mirror tilt angle is increased to achieve higher attenuation, then the optical attenuation is improved, but the WDL increases
Solution Approach 1:
The patent applies preliminary anti-action by pre-compensating for WDL through the gap design and stress elimination. By preventing the generation of additional WDL through radial stress, the system can achieve higher attenuation through mirror tilt without the harmful side effect of increased WDL that would otherwise occur.
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 approach effectively reduces PDL and WDL, enhancing the reliability and consistency of the variable optical attenuator by minimizing stress-induced losses and allowing real-time WDL compensation during assembly.
Implementation Method 1
a lens 11, fixed to the front end of the pigtail to focus the incident light from the first waveguide of the pigtail 10 and to make the reflected light return to the second waveguide of the pigtail 10
Implementation Method 2
a chip 15 with a rotating mirror, fixed to a header 14 to reflect the incident light passing the lens from the first waveguide, and make the reflected light pass through the lens to return to the second waveguide
Data Source
AI summary
Provided is a variable optical attenuator, including a pigtail, a spacer, a lens and a cap. The pigtail has a first waveguide and a second waveguide. The first waveguide transmits incident light, and the second waveguide receives the returned light. The pigtail is attached to one side of the space, and the lens is attached to another side of the space. Moreover, the cap includes a hollow portion, a first connecting portion and a second connecting portion. The lens is placed inside the hollow portion, and the space is connected to the first connecting portion of the cap.