US-12621057-B2 - Auto tuning of DWDM wavelength of transponder connected to colored passive multiplexing modules

US12621057B2US 12621057 B2US12621057 B2US 12621057B2US-12621057-B2

Abstract

A method for auto-tuning an optical transponder that is coupled to an optical terminal comprises: cycling through wavelengths in sequence by, for each wavelength: modulating the wavelength to convey a wavelength identifier of the wavelength, to produce a modulated wavelength that conveys the wavelength identifier; transmitting the modulated wavelength from the optical terminal through an optical demultiplexer that is configured to pass wavelengths to output ports of the optical demultiplexer; waiting to detect a response wavelength, transmitted by the optical transponder, which matches the wavelength; and determining, based on whether the response wavelength is detected, whether to repeat cycling using a next wavelength because the optical transponder is not tuned or to stop cycling because the optical transponder is tuned.

Inventors

Richard Moses Samuel
Marco Liri
Lokesh Kumar Thirumakudalu Nagaraju
Stefano Andrea Pezzoli
Vishwakarma Pooja Ramashankar

Assignees

CISCO TECHNOLOGY, INC.

Dates

Publication Date: 20260505
Application Date: 20230201

Claims (20)

1 . A method of auto-tuning an optical transponder coupled to an optical terminal, comprising: cycling through wavelengths in sequence by, for each wavelength: modulating the wavelength to convey a wavelength identifier of the wavelength, to produce a modulated wavelength that conveys the wavelength identifier; transmitting the modulated wavelength from the optical terminal through an optical demultiplexer that is configured to pass modulated wavelengths to output ports of the optical demultiplexer; waiting to detect a response wavelength, transmitted by the optical transponder, which matches the wavelength; determining, based on whether the response wavelength is detected, whether to repeat cycling using a next wavelength because the optical transponder is not tuned or to stop cycling because the optical transponder is tuned; and by the optical transponder: upon receiving the modulated wavelength, recovering the wavelength identifier; and tuning the optical transponder to operate at the wavelength based on the wavelength identifier.
2 . The method of claim 1 , wherein determining whether to repeat cycling with the next wavelength or to stop cycling includes: when the response wavelength is not detected, which indicates that the optical transponder is not tuned, repeating cycling using the next wavelength; and when the response wavelength is detected, which indicates that the optical transponder is tuned, stopping cycling.
3 . The method of claim 1 , wherein: waiting to detect the response wavelength includes waiting to detect the response wavelength only for a predetermined period of time; and determining includes determining whether to repeat cycling using the next wavelength or to stop cycling based on whether the response wavelength is detected within the predetermined period of time.
4 . The method of claim 1 , wherein: the optical demultiplexer is configured to pass the wavelengths selectively from an input port of the optical demultiplexer that is coupled to the optical terminal to corresponding ones of the output ports of the optical demultiplexer; an optical multiplexer to pass the wavelengths selectively from corresponding ones of input ports of the optical multiplexer to an output port of the optical multiplexer that is coupled to the optical terminal; transmitting includes transmitting the modulated wavelength through one of the output ports of the optical demultiplexer that corresponds to the wavelength; and waiting to detect the response wavelength includes waiting to detect the response wavelength through one of the input ports of the optical multiplexer that corresponds to the wavelength.
5 . The method of claim 1 , wherein: modulating includes tone modulating the wavelength with a tone pattern indicative of the wavelength identifier.
6 . The method of claim 1 , further comprising multiple optical transponders coupled to the optical terminal through multiple output ports of the output ports of the optical demultiplexer, and the method further comprises: repeating auto-tuning for each of the multiple optical transponders.
7 . The method of claim 1 , wherein the optical transponder includes an optical receiver and a tone detector coupled to one of the output ports of the optical demultiplexer, and an optical transmitter coupled to an input port of input ports of a multiplexer having an output port coupled to the optical terminal, and wherein: receiving the modulated wavelength includes receiving the modulated wavelength via the tone detector, recovering the wavelength identifier; and tuning the optical transponder includes tuning the optical transmitter and the optical receiver to operate at the wavelength.
8 . The method of claim 7 , further comprising, at the optical transponder: by the optical transmitter, after tuning, transmitting the wavelength.
9 . The method of claim 1 , further comprising: when the wavelength is detected, which indicates that the optical transponder is tuned, performing an end-to-end circuit check for the optical transponder, the end-to-end circuit check including exchanging optical frames using the wavelength with a far-end optical transponder through the optical terminal.
10 . The method of claim 1 , wherein the optical transponder includes an optical receiver and an optical transmitter that are each configured to process optical signals having a dense wavelength-division multiplexing (DWDM) spectrum.
11 . An apparatus comprising: a tunable laser and tone generator module; an optical channel monitor; and a controller configured to control the tunable laser and tone generator module and the optical channel monitor to auto-tune an optical transponder that is coupled to the apparatus by: cycling through wavelengths in sequence by, for each wavelength: causing the tunable laser and tone generator module to modulate the wavelength to convey a wavelength identifier of the wavelength, to produce a modulated wavelength that conveys the wavelength identifier; causing the tunable laser and tone generator module to transmit the modulated wavelength through an optical demultiplexer that is configured to pass modulated wavelengths to output ports of the optical demultiplexer; waiting for the optical channel monitor to detect a response wavelength, transmitted by the optical transponder, which matches the wavelength; determining, based on whether the response wavelength is detected, whether to repeat cycling using a next wavelength because the optical transponder is not tuned or to stop cycling because the optical transponder is tuned; and upon detecting the response wavelength, which indicates that the optical transponder is tuned, performing an end-to-end circuit check for the optical transponder, the end-to-end circuit check including exchanging optical frames using the wavelength with a far-end optical transponder through the apparatus.
12 . The apparatus of claim 11 , wherein the controller is configured to perform determining whether to repeat cycling with the next wavelength or to stop cycling by: when the response wavelength is not detected, which indicates that the optical transponder is not tuned, repeating cycling using the next wavelength; and when the response wavelength is detected, which indicates that the optical transponder is tuned, stopping cycling.
13 . The apparatus of claim 11 , wherein: the controller is configured to perform waiting by waiting for the optical channel monitor to detect the response wavelength only for a predetermined period of time; and the controller is configured to perform determining by determining whether to repeat cycling using the next wavelength or to stop cycling based on whether the response wavelength is detected within the predetermined period of time.
14 . The apparatus of claim 11 , wherein: the optical demultiplexer is configured to pass the wavelengths selectively from an input port of the optical demultiplexer that is coupled to the apparatus to corresponding ones of the output ports of the optical demultiplexer; an optical multiplexer to pass the wavelengths selectively from corresponding ones of input ports of the optical multiplexer to an output port of the optical multiplexer that is coupled to the apparatus; the tunable laser and tone generator module is configured to transmit the modulated wavelength through one of the output ports of the optical demultiplexer that corresponds to the wavelength; and the controller is configured to perform waiting by waiting to detect the response wavelength through one of the input ports of the optical multiplexer that corresponds to the wavelength.
15 . The apparatus of claim 11 , wherein: the tunable laser and tone generator module is configured to tone modulate the wavelength with a tone pattern indicative of the wavelength identifier.
16 . The apparatus of claim 11 , further comprising multiple optical transponders coupled to the apparatus through multiple output ports of the output ports of the optical demultiplexer, and the controller is further configured to: repeat auto-tuning for each of the multiple optical transponders.
17 . The apparatus of claim 11 , wherein: the wavelength identifier includes a digital code.
18 . A system comprising: an optical transponder; and an optical terminal configured to auto-tune the optical transponder by: cycling through wavelengths in sequence, and for each wavelength: modulating the wavelength to convey a wavelength identifier of the wavelength, to produce a modulated wavelength; transmitting the modulated wavelength through an optical demultiplexer that is configured to pass the modulated wavelengths to output ports of the optical demultiplexer, one of the output ports being coupled to the optical transponder; waiting to detect a response wavelength, transmitted by the optical transponder, which matches the wavelength; and determining, based on whether the response wavelength is detected, whether to repeat cycling using a next wavelength because the optical transponder is not tuned or to stop cycling because the optical transponder is tuned, wherein the optical transponder is configured to perform: upon receiving the modulated wavelength, recovering the wavelength identifier; tuning the optical transponder to the wavelength based on the wavelength identifier; and transmitting the wavelength as the response wavelength.
19 . The system of claim 18 , wherein the optical terminal is configured to perform determining whether to repeat cycling with the next wavelength or to stop cycling by: when the response wavelength is not detected, which indicates the optical transponder is not tuned, repeating cycling using the next wavelength; and when the response wavelength is detected, which indicates the optical transponder is tuned, stopping cycling.
20 . The system of claim 18 , wherein: tuning the optical transponder includes tuning an optical receiver and an optical transmitter of the optical transponder.

Description

TECHNICAL FIELD The present disclosure relates generally to optical networks. BACKGROUND Wavelength tunable optical transponders deployed at geographically separated optical sites may exchange optical signals with each other through optical wavelength selective (i.e., “colored”) input and output ports of colored passive optical multiplexing modules that are connected to the optical transponders over a fiber patch cord. Often, the optical transponders do not know to which of the wavelength selective input and output ports the optical transponders are connected, which means that the optical transponders do not know the correct wavelengths at which to transmit and receive the optical signals to ensure their delivery through the colored passive optical multiplexing modules. That is, the optical transponders may not be tuned to transmit and receive optical signals at the correct wavelengths. A conventional tuning technique includes manually tuning the optical transponders to transmit and receive the optical signals at wavelengths matched to the wavelength selective input and output ports to which the optical transponders are connected; however, this approach is time consuming and inefficient. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an optical network in which embodiments for automatically (auto)-tuning wavelengths at which optical transponders operate may be implemented, according to an example embodiment. FIG. 2 is a block diagram of an optical site from FIG. 1 that shows details of an optical terminal and an optical transponder useful for describing operations used to perform the auto-tuning, according to an example embodiment. FIG. 3A is a flowchart of a method of auto-tuning optical transponders performed primarily by the optical terminal, according to an example embodiment. FIG. 3B is an illustration of a data word used to tone modulate a wavelength with a wavelength identifier, according to an example embodiment, FIG. 4 is a flowchart of a method performed by the optical terminal in the background while the method of FIG. 3A is performed, according to an example embodiment. FIG. 5 is a flowchart of a method performed by the optical transponder in connection with the method of FIG. 3A, according to an example embodiment. FIG. 6 is a diagram of an arrangement of components in the optical network used to perform an end-to-end circuit check between optical transponders after the optical transponders have been auto-tuned, according to an example embodiment. FIG. 7 is a flowchart of another method of auto-tuning an optical transponder performed primarily by the optical terminal, according to an example embodiment. FIG. 8 illustrates a hardware block diagram of a computing device that may perform functions associated with operations discussed herein, according to an example embodiment. DETAILED DESCRIPTION Overview In an embodiment, a method for auto-tuning an optical transponder that is coupled to an optical terminal is performed. The method comprises: cycling through wavelengths in sequence by, for each wavelength: modulating the wavelength to convey a wavelength identifier of the wavelength, to produce a modulated wavelength that conveys the wavelength identifier; transmitting the modulated wavelength from the optical terminal through an optical demultiplexer that is configured to pass wavelengths to output ports of the optical demultiplexer; waiting to detect a response wavelength, transmitted by the optical transponder, which matches the wavelength; and determining whether to repeat cycling using a next wavelength or to stop cycling based on whether the response wavelength is detected. Example Embodiments FIG. 1 is a block diagram of an example optical network 100 in which embodiments directed to auto-tuning wavelengths at which optical transponders operate, when the optical transponders are connected to colored passive optical multiplexing modules, may be implemented. Such auto-tuning represents a convenient “plug-and-play” method of tuning the optical transponders. The method advantageously avoids manual intervention and the use of a patch cord connection for tuning. Optical network 100 includes an optical site 102 deployed at a first site location and an optical site 104 deployed at a second site location that is geographically separated from the first site location. Optical sites 102 and 104, including their corresponding optical components described below, may be configured to process, transmit, and receive optical signals having dense wavelength-division multiplexing (DWDM) optical spectrums, for example. For the present description, it is understood that a particular wavelength λ corresponds to a particular frequency f through the relationship f·λ=c, where c is the speed of light. Also, the terms “wavelength” and “frequency” may be used interchangeably, depending on context. Optical site 102 includes an optical line terminal (OLT) 110 (more generally referred to as an “optical t