Low Latency Dispersion Compensation Modules for Extended Reach Optical Networks
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Solution Overview
Problem
Current low differential latency optical systems face challenges in extending reach beyond 100 km due to additional time delays introduced by optical amplifiers and dispersion compensation modules, which make it difficult to maintain the required latency specifications of +/−5 μs in systems like IBM's Geographically-Dispersed Parallel Sysplex (GDPS) and Server Time Protocol (STP).
Innovation Solution
The implementation of low latency dispersion compensation modules, such as channelized etalon or fiber Bragg grating-based modules, and the use of bidirectional systems with shared amplifiers and dispersion compensation modules, along with mechanisms for measuring and selectively compensating for differential delays, to minimize latency between transmit and receive paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional dispersion compensation modules based on dispersion-compensating fiber are used to extend reach beyond 100 km, then the transmission distance is improved, but the latency increases significantly (up to 70 μs) and differential latency control becomes difficult
Solution Approach 1:
The patent changes the fundamental parameter of dispersion compensation from using long dispersion-compensating fiber (which causes high latency) to using gratings (which provide low latency). This parameter change allows achieving the same dispersion compensation function with dramatically reduced time delay, enabling extended reach while maintaining low latency requirements.
Solution Approach 2:
The patent substitutes the mechanical/fiber-based dispersion compensation approach (using dispersion-compensating fiber) with an optical grating-based approach. This substitution replaces the physical fiber winding method with a grating structure that achieves dispersion compensation through optical interference principles, resulting in lower latency.
2Length of stationary object
If optical amplifiers and dispersion compensation modules are added to extend reach beyond 100 km, then the transmission distance is improved, but the device complexity and cost increase
Solution Approach 1:
The patent changes the dispersion compensation technology parameter from conventional fiber-based methods to grating-based methods. This parameter change simplifies the overall system architecture by enabling extended reach with lower complexity components, as gratings can be integrated more compactly and with fewer auxiliary systems compared to long DCF modules.
3Loss of time
If fiber lengths are matched to within 1 km to maintain low differential latency, then the latency specification is met, but the system reach is limited to less than 100 km
Solution Approach 1:
The patent changes the dispersion compensation approach to use gratings with specifically engineered group delay characteristics. This parameter change allows the system to compensate for dispersion over long distances while maintaining controlled and predictable latency, thereby breaking the limitation that prevented extending reach beyond 100 km while maintaining low differential latency.
Solution Approach 2:
The patent applies preliminary dispersion compensation using gratings at strategic points in the transmission path. By pre-compensating for dispersion accumulation before it becomes problematic, the system can extend reach beyond 100 km while maintaining the tight latency specifications required for STP protocols.
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 allows for extended reach low differential latency optical networking, maintaining the required latency specifications of +/−5 μs even beyond 100 km, ensuring accurate clock time synchronization between servers in multi-site enterprises, and reducing the cost and complexity of amplifiers and dispersion compensation modules.
Implementation Method 1
at least one dispersion compensation module, and wherein the at least one fiber amplifier and the at least one dispersion compensation module are configured to minimize differential latency
Implementation Method 2
at least one fiber amplifier, and wherein the at least one fiber amplifier and the at least one dispersion compensation module are operative to extend the reach of the telecommunications transport system
Data Source
AI summary
Systems and methods for extended reach low differential latency optical networking with optical amplifiers and dispersion compensation modules configured to minimize latency between transmit and receive paths are provided. Additionally, systems and methods are provided for incorporating absolute time references wherein the relative accuracy of clock time between various servers used in various multi-site enterprises is required. The transport systems and methods are used in conjunction with low differential latency systems. The transport systems and methods provide that the differential latency between transmit and receive directions is maintained within about +/−5 microseconds of the transmit/receive path differential delay requirement in order to perform within the overall parameters of the low differential latency system architecture.