Dispersionless Optical Tap Filter for Multimode Fiber Links
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Solution Overview
Problem
Multimode fused optical couplers experience mode dispersion and tap-ratio control issues in high-speed networks, leading to insertion loss degradation and limited data bandwidth, especially at speeds above 10 Gbps, due to non-symmetry tapping/splitting ratios and wavelength-dependent coupling.
Innovation Solution
A dispersionless multimode optical tap filter using a broadband thin film filter and dual fiber collimators, which taps out monitoring signals with a ratio set by the thin film filter, eliminating mode sensitivity and allowing independent control of tap ratios for different wavelengths, thus addressing mode dispersion and tap-ratio control challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multimode fused optical coupler is used for signal monitoring, then the device can split and monitor optical signals, but mode dispersion occurs leading to insertion loss degradation and limited data bandwidth at high speeds
Solution Approach 1:
The patent changes the fundamental operating parameters by using single-mode fiber instead of multimode fiber, and by employing wavelength division multiplexing with specific wavelength pairs (850nm/910nm or 1310nm/1550nm). This parameter change eliminates mode dispersion while enabling high-speed operation above 10 Gbps, resolving the contradiction between monitoring reliability and transmission speed
Solution Approach 2:
The patent introduces wavelength division multiplexing as an intermediary mechanism, using different wavelengths for signal and monitor channels. This allows the monitoring function to be separated from the high-speed data channel, eliminating mode dispersion effects on the data transmission while maintaining monitoring capability
2Adaptability or versatility
If non-symmetry tapping/splitting ratio is used in multimode coupler, then different wavelengths can have different tap ratios, but wavelength-dependent coupling causes mode oriented insertion loss degradation
Solution Approach 1:
The patent changes the fiber type parameter from multimode to single-mode, which eliminates wavelength-dependent mode coupling effects. This allows flexible tap ratio control for different wavelengths without suffering from mode oriented insertion loss degradation, as single-mode fiber does not exhibit modal dispersion
Solution Approach 2:
The patent replaces the fused fiber coupler mechanism with a thin-film filter-based wavelength division multiplexing system. This substitution provides precise, independent control of tap ratios for different wavelengths through the thin-film filter design, eliminating the wavelength-dependent coupling issues inherent in fused multimode couplers
3Productivity
If multimode fiber is used for high-speed parallel data links, then VCSEL technology can transmit multiple channels, but modal dispersion limits the data bandwidth especially for non-50/50 coupler ratios
Solution Approach 1:
The patent changes the fiber mode parameter from multimode to single-mode in the monitoring path, eliminating modal dispersion. This allows the system to maintain high parallel channel capacity from VCSELs while achieving reliable high-bandwidth monitoring without the data bandwidth limitations imposed by modal dispersion in multimode couplers
Solution Approach 2:
The patent segments the optical signal into different wavelength channels using wavelength division multiplexing, with separate signal and monitor wavelengths. This segmentation allows the high-speed data channels to operate in multimode fiber while the monitoring function operates in single-mode fiber, avoiding modal dispersion effects on the monitoring bandwidth
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 stable monitoring of optical power and mode distribution in high-speed multimode fiber communications, enabling efficient data transmission without mode dispersion and allowing flexible tap ratio tuning, suitable for high-speed applications up to 8 Gbps and beyond.
Implementation Method 1
a broadband thin film filter and taps out a monitoring signal from a communication signal according to a ratio set by the broadband thin film filter
Implementation Method 2
the broadband thin film filter transmits a portion of the first light beam at the first wavelength to the second port of the second part and reflects remaining of the first light beam to the second port of the first part
Implementation Method 3
a first dual fiber collimator including first and second ports; a second part including a second dual fiber collimator including first and second ports
Data Source
AI summary
Techniques for monitoring optical power, dispersion and mode distribution in high speed multimode fiber are described. According to one aspect of the present invention, a multimode optical tap filter is described. In one aspect of the present invention, an optical tap filter is a dispersionless optical tap filter in bi-directional multimode fiber optic link. The optical tap filter includes at least two parts optically engaged with a broadband thin film filter and taps out a monitoring signal from a communication signal according to a ratio set by the broadband thin film filter.