Modal Delay and Bandwidth Measurement for Optical Fibers
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Solution Overview
Problem
Standard single mode (SM) fibers are preferred in hyperscale data centers for their higher bandwidth and longer distance data transmission, but for short links, managing two types of fiber cables increases complexity and costs, while multimode (MM) fibers with vertical-cavity surface-emitting lasers (VCSELs) offer lower cost and power consumption, but with chromatic dispersion limitations.
Innovation Solution
A method and system for measuring modal delay and modal bandwidth in optical fibers by transmitting intensity-modulated light through a mode conditioner, converting it into an electrical signal, and calculating transfer functions to determine modal delay and bandwidth, suitable for SM or few-mode fibers, optimizing bandwidth for the 850 nm to 1100 nm wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If standard single mode fiber is used for both long and short data links, then fiber cable management is simplified, but the cost and complexity of managing two different fiber types increases
Solution Approach 1:
The patent makes standard single-mode fiber universally applicable for both short and long data links by enabling few-mode operation at 850nm wavelength. The fiber can support single-mode operation for long distances and few-mode operation for short distances, eliminating the need to manage separate multimode fibers for short links.
2Ease of manufacture
If multimode fiber with VCSEL transceivers is used for short data links, then cost and power consumption are reduced, but chromatic dispersion limits bandwidth performance
Solution Approach 1:
The patent changes the operational parameters by using standard single-mode fiber in a wavelength range (850nm-1100nm) where it supports few modes instead of its conventional single-mode operation above 1300nm. This parameter change enables VCSEL-based low-cost transceivers to achieve high bandwidth performance previously only available with expensive laser sources.
3Adaptability or versatility
If standard single mode fiber is used in the 850nm to 1100nm wavelength range, then VCSEL transmission is enabled, but bandwidth is too low for high data rate transmission
Solution Approach 1:
The patent introduces dynamically adjustable mode conditioners that can adapt the launch conditions to optimize mode excitation. This dynamic control enables the system to achieve high bandwidth performance by properly conditioning the light launch into the few-mode fiber, transforming it from unsuitable to optimal for high data rate transmission.
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
Enables low-cost optical transmission over SM fibers for short links by optimizing modal bandwidth, reducing fiber cable management complexities and enhancing data rate performance without the need for expensive time-domain measurement instruments.
Implementation Method 1
converting the mode-conditioned intensity-modulated light transmitted through the optical FUT into an electrical signal
Data Source
AI summary
The present disclosure is directed to systems and methods for calculating a modal time delay and a modal bandwidth. For example, a method may include: transmitting an intensity-modulated light through a mode conditioner to generate a mode-conditioned intensity-modulated light; transmitting the mode-conditioned intensity-modulated light through an optical fiber under test (FUT) to excite a plurality of modes of the optical FUT; converting the mode-conditioned intensity-modulated light transmitted through the optical FUT into an electrical signal; measuring, based on the electrical signal, a transfer function or a complex transfer function of the optical FUT based on at least on one pair of the plurality of modes; calculating a modal delay time of the optical FUT based on the transfer function or the complex transfer function; and calculating a modal bandwidth of the optical FUT based on the modal delay time, the modal bandwidth being calculated for any given launch conditions of the plurality of modes.