Optical Path Latency Measurement Using Supervisory Channel
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining the latency or length of an optical path in fiber-optical transmission links are costly, require synchronized clocks, and disrupt data transmission, making them inefficient for real-time measurements in optical networks.
Innovation Solution
A method using a bidirectional optical supervisory channel to measure round-trip delay by transmitting measurement bits or patterns between nodes, calculating the total round-trip delay, and compensating for signal processing delays to determine the optical path length without the need for synchronized clocks, allowing for low-cost, non-disruptive measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical time domain reflectometer (OTDR) measurement equipment is used to measure fiber length, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent enables optical transmission systems to perform their own latency measurements using built-in time stamps and counters. Each optical transmission system generates time stamps when sending packets and measures the round-trip time using its own clock, eliminating the need for external OTDR equipment. This self-measurement capability resolves the contradiction by providing adequate measurement functionality without requiring complex external measurement devices.
2Measurement precision
If synchronized clocks are used on both ends of the transmission link for latency measurement, then measurement precision is improved, but device complexity and synchronization requirements increase
Solution Approach 1:
Instead of requiring synchronized clocks at both ends to measure one-way latency, the patent inverts the approach by measuring round-trip latency using a single unsynchronized clock at one end. The system sends a packet with a time stamp, receives the echoed packet, and calculates the round-trip time using only its own clock. This inversion eliminates the need for complex clock synchronization while providing sufficient measurement accuracy for network operations.
3Measurement precision
If dedicated measurement equipment or protocols are used for latency measurement, then measurement accuracy is improved, but ease of operation decreases due to disruption of data transmission
Solution Approach 1:
The patent merges measurement functionality with normal data transmission by using the same optical channels and protocols. Latency measurement packets are transmitted using the existing optical transmission infrastructure without requiring separate measurement channels. The measurement process is integrated into the regular data flow, allowing continuous operation without disruption and maintaining ease of operation while achieving measurement accuracy.
4Measurement precision
If multiple round-trip measurements are performed to determine optical path length, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs a sufficient number of round-trip measurements to achieve the required measurement precision without unnecessarily extending measurement time. By conducting multiple measurements and averaging the results, the system obtains accurate optical path length values while limiting the total measurement duration. This balanced approach provides adequate precision for network operations without excessive time loss.
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 accurate and cost-effective determination of optical path length without affecting data transmission, facilitating efficient routing and dispersion compensation in optical networks.
Implementation Method 1
transmitting, within the optical supervisory channel, measurement bits or bit patterns forth and back between a first and second end of an optical path
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
The invention relates to a method for determining the latency or length of an optical path, especially an optical fiber, of a fiber-optic transmission link, the method comprising the steps of: starting a measurement cycle at a first point in time (T1), wherein, for carrying out the measurement, measurement bits or bit patterns are transmitted forth and back within an optical supervisory channel between a first and second end of the optical path (105), beginning at the first end at the first point in time (T1), for a predetermined number (N) of round trips; stopping the measurement cycle at a second point in time (T2) after having received a last measurement bit or bit pattern at the first end; determining, at the first end, the total round-trip delay (RTDi; RTDcor,l, 1≤i≤N) of the optical path by evaluating a time information (T1, T2, T3, T4, ΔTel) available at the first end, wherein the time information (T1, T2, T3, T4, ΔTel) at least comprises the first and second points in time (T1, T2), and taking into account the predetermined number (N) of round-trips; and optionally calculating the length (ΔL) of the optical path (105) by using the total round-trip delay (RTDi; RTDcor,l) and the group velocity vg characterizing the signal propagation along the optical path (105). Further, the invention relates to a device for implementing the method and to an optical transmission link (100) comprising such a device as well as to a method and an optical network (200) for routing signals, wherein latency constraints are fulfilled.