Determination of the latency of an optical transmission link

Patent metadata

Field	Value
Publication number	US-10958995-B2
Application number	US-201916701588-A
Country	US
Kind code	B2
Filing date	Dec 3, 2019
Priority date	Dec 13, 2018
Publication date	Mar 23, 2021
Grant date	Mar 23, 2021

Abstract

Disclosed is a method for determining the link latency of an optical transmission link which includes an end node at each end and one or more pass-through nodes. Each pair of neighboring nodes is connected, at a connection port of each node, by an optical connecting path. Each pass-through node includes an optical pass-through path between its connection ports. The optical connecting paths and optical pass-through paths form an optical link path. A delimiter device includes a delimiter element provided at each connection port of each node. The delimiter element forms a demarcation within the optical link path. According to the method the following steps are carried out: measuring, for each pair of neighboring nodes, a section latency by transmitting a section probe signal from a first one of the pair of nodes to the second one of the pair of nodes; measuring, at the first node, a first time delay of a first reflection signal, which is created by the delimiter element of the delimiter device of the first node by reflecting a power portion of the section probe signal, and a second time delay of a second reflection signal, which is created by the delimiter element of the delimiter device of the second node by reflecting a power portion of the section probe signal received from the first node; and calculating the section latency as half the difference between the second time delay and the first time delay; determining, for each pass-through node either theoretically or by measurement, a pass-through latency of an internal optical pass-through path between the delimiter elements of the delimiter devices of the respective pass-through node; and adding all section latencies and pass-through latencies in order to obtain the link latency of the optical link path.

First claim

The invention claimed is:

1. A method for determining the link latency of an optical transmission link,
(a) wherein the optical transmission link comprises an end node at each end thereof and one or more pass-through nodes, wherein each pair of neighboring nodes is connected, at a connection port of each node, by an optical connecting path, and wherein each pass-through node comprises an optical pass-through path between its connection ports, the optical connecting paths and optical pass-through paths forming an optical link path, and
(b) wherein a delimiter device comprising a delimiter element is provided at each connection port of each node, and wherein the delimiter element forms a demarcation within the optical link path,
the method comprising the steps of:
(c) measuring, for each pair of neighboring nodes, a section latency by
(i) transmitting a section probe signal from a first one of the pair of nodes to the second one of the pair of nodes,
(ii) measuring, at the first node, a first time delay of a first reflection signal, which is created by the delimiter element of the delimiter device of the first node by reflecting a power portion of the section probe signal, and a second time delay of a second reflection signal, which is created by the delimiter element of the delimiter device of the second node by reflecting a power portion of the section probe signal received from the first node, and
(iii) calculating the section latency as half the difference between the second time delay and the first time delay,

(d) determining, for each pass-through node either theoretically or by measurement, a pass-through latency of an internal optical pass-through path between the delimiter elements of the delimiter devices of the respective pass-through node, and
(e) adding all section latencies and pass-through latencies in order to obtain the link latency of the optical link path.

2. The method according to claim 1 , wherein the pass-through latency of a bidirectional internal optical pass-through path of a pass-through node is determined by
(a) feeding, at a start time, the pass-through probe signal, via a probe signal path, to a first one of the delimiter devices,
(b) measuring, relative to the start time or another reference time, a first time delay of a first reflection signal created by the first delimiter device by reflecting a power portion of the pass-through probe signal into the probe signal path,
(c) measuring, relative to the start time or another reference time, a second time delay of a second reflection signal created by a second one of the delimiter devices by reflecting a power portion of the pass-through probe signal that is transmitted by the first delimiter device to the second delimiter device via the optical pass-through path, wherein the first delimiter device is configured to transmit a power portion of the pass-through probe signal reflected by the second delimiter device to the probe signal path,
(d) or by directly measuring the time delay between the first and second reflection signal, and
(e) calculating the pass-through latency as half the difference between the separately measured second and first time delay or as half the directly measured time delay.

3. The method according to claim 1 , wherein the pass-through latency of a unidirectional or bidirectional optical pass-through path of a pass-through node, which comprises a common probe signal path that is split into a first probe signal path connected to a first one of the delimiter devices and a second probe signal path connected to a second one of the delimiter devices, is determined by
(a) measuring a first time delay of a reflection signal created by the first one of the delimiter devices by reflecting, into the first probe signal path, a power portion of a pass-through probe signal that is fed to the common probe signal path,
(b) measuring a second time delay of a reflection signal created by the second one of the delimiter devices by reflecting, into the second probe signal path, a power portion of the same or another pass-through probe signal,
(c) measuring a third time delay of a transmission signal created by feeding the same or another pass-through probe signal to the first delimiter device, which is configured to transmit a power portion of the pass-through probe signal, via the internal optical pass-through path, to the respective other delimiter device, which is configured to transmit at least a power portion of the pass-through probe signal received, as the transmission signal, to the second probe signal path, and
(d) calculating the pass-through latency as the difference of the third time delay and half the sum of the first time delay and the second time delay.

4. The method according to claim 3 , wherein
(a) the measurement of the first time delay is carried out using one or more first pass-through probe signals, wherein the second probe signal path is blocked during this measurement step, e.g. by means of an optical switch, that the measurement of the second time delay is carried out using one or more second pass-through probe signals, wherein the first probe signal path is blocked during this measurement step, e.g. by means of an optical switch, and that the measurement of the third time delay is carried out using one or more third pass-through probe signals, and wherein the first and second probe signal path are not blocked during this measurement step.

5. The method according to claim 1 , wherein the section or pass-through probe signals have a wavelength equal to a wavelength of a wanted data signal that is transmitted over the optical transmission link when it is in operation, wherein determining of the section and node latencies is carried out when the optical transmission link is out of service.

6. The method according to claim 1 , wherein the section or pass-through probe signals have a wavelength outside a bandwidth that is reserved for wanted data signals that are transmitted over the optical transmission link when it is in operation, and wherein determining of the section and node latencies is carried out when the optical transmission link is in or out of service.

7. The method according to claim 6 , wherein the optical transmission link is monitored by carrying out the method on request or at predetermined points in time.

8. The method according to claim 6 , wherein each section and pass-through latency is determined at two or more different wavelengths, preferably at at least one wavelength above and below a wavelength of a wanted data signal or the bandwidth that is reserved for wanted data signals, and wherein the section or pass-through latencies are calculated using linear or non-linear interpolation or an analytical dependency of the respective section or pass-through latency on the wavelength taking into account known properties or parameters of the connecting paths or the optical pass-through paths.

9. An optical transmission link comprising
(a) an end node at each end thereof and one or more pass-through nodes and a central control device, which is connected to selected ones of the end nodes and pass-through nodes, wherein a first node of each pair of neighboring nodes comprises a first connection port and a second node of the respective pair of neighboring nodes comprises a second connection port, the first and second connection ports being connected by an optical connecting path, and wherein each pass-through node comprises an optical pass-through path which optically connects its connection ports, the optical connecting paths and optical pass-through paths forming an optical link path,
(b) wherein a first node of each pair of neighboring nodes comprises
(i) an optical probe signal transceiver configured to create

Assignees

• Adva Optical Networking Se

Inventors

• Eiselt Michael

Classifications

• H04J14/02

  Wavelength-division multiplex systems · CPC title

• H04B10/071

  using a reflected signal, e.g. using optical time domain reflectometers [OTDR] · CPC title

• H04B10/0775

  Performance monitoring and measurement of transmission parameters · CPC title

• H04B10/07 Primary

  Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems · CPC title

• H04Q2213/13164

  Traffic (registration, measurement,...) · CPC title