US-20260128790-A1 - OPTICAL TRANSMISSION SYSTEM AND QUALITY ESTIMATION METHOD

US20260128790A1US 20260128790 A1US20260128790 A1US 20260128790A1US-20260128790-A1

Abstract

An optical transmission system includes a first optical transmission device that transmits a first signal light in an actual operation and a first pseudo light having a wavelength different from that of the first signal light, a second optical transmission device that receives the first signal light and the first pseudo light from the first optical transmission device, a measurer that measures a first quality of the first pseudo light between the first optical transmission device and the second optical transmission device, and an estimator that estimates a second quality of the first signal light between the first optical transmission device and the second optical transmission device based on the first quality and an indicator value of wavelength dependence in a signal band.

Inventors

Kentaro KAWANISHI
Hiroki Ooi
Goji Nakagawa

Assignees

1FINITY INC.

Dates

Publication Date: 20260507
Application Date: 20251024
Priority Date: 20241107

Claims (13)

1 . An optical transmission system comprising: a first optical transmission device that transmits a first signal light in an actual operation and a first pseudo light having a wavelength different from that of the first signal light; a second optical transmission device that receives the first signal light and the first pseudo light from the first optical transmission device; a measurer that measures a first quality of the first pseudo light between the first optical transmission device and the second optical transmission device; and an estimator that estimates a second quality of the first signal light between the first optical transmission device and the second optical transmission device based on the first quality and an indicator value of wavelength dependence in a signal band.
2 . The optical transmission system according to claim 1 , wherein the second optical transmission device has an optical channel monitor, the first optical transmission device switches between emission of the first pseudo light and emission stop of the first pseudo light, and the measurer measures the first quality based on a first measurement value by the optical channel monitor at the time of the emission and a second measurement value by the optical channel monitor at the time of the emission stop.
3 . The optical transmission system according to claim 1 , wherein the first quality and the second quality are an optical signal-to-noise ratio.
4 . The optical transmission system according to claim 1 , wherein the indicator value indicates a correspondence relationship between a plurality of wavelengths and at least the first quality, the plurality of wavelengths including a wavelength of the first signal light and a wavelength of the first pseudo light.
5 . The optical transmission system according to claim 1 , wherein the indicator value is measured before an operation of an optical communication service performed between the first optical transmission device and the second optical transmission device based on the first signal light is started.
6 . The optical transmission system according to claim 1 , further comprising: a third optical transmission device that receives the first pseudo light from the first optical transmission device, switches a received first pseudo light to a second pseudo light having a wavelength different from that of the first pseudo light, and transmits the second pseudo light to the second optical transmission device, wherein the measurer measures a third quality of the first pseudo light between the first optical transmission device and the third optical transmission device and a fourth quality of the second pseudo light between the third optical transmission device and the second optical transmission device, and wherein the estimator estimates the second quality based on the third quality, the fourth quality, and the indicator value.
7 . The optical transmission system according to claim 1 , further comprising: a third optical transmission device that receives the first pseudo light from the first optical transmission device, switches a received first pseudo light to a second signal light having any wavelength belonging to a wavelength of the first pseudo light, and transmits the second signal light to the second optical transmission device, wherein the measurer measures a third quality of the first pseudo light between the first optical transmission device and the third optical transmission device, and wherein the estimator estimates the second quality based on the third quality and the indicator value.
8 . The optical transmission system according to claim 7 , wherein the measurer further measures a span loss of the first pseudo light between the first optical transmission device and the second optical transmission device, and the estimator estimates the second quality based on at least one of the first quality, the span loss, the indicator value, and an input optical power of a second signal light having a wavelength belonging to a wavelength of the first pseudo light to the second optical transmission device.
9 . The optical transmission system according to claim 7 , wherein the measurer calculates a fifth quality of the second signal light between the third optical transmission device and the second optical transmission device based on an input optical power of the second signal light to the second optical transmission device and a specification value of an optical amplifier provided in the second optical transmission device, and the estimator estimates the second quality based on the third quality, the fifth quality, and the indicator value.
10 . The optical transmission system according to claim 1 , wherein the measurer or the estimator is provided in at least one of the first optical transmission device, the second optical transmission device, a third optical transmission device positioned between the first optical transmission device and the second optical transmission device, and a controller that controls operations of the first optical transmission device, the second optical transmission device, and the third optical transmission device.
11 . The optical transmission system according to claim 1 , wherein the measurer further measures a span loss of the first pseudo light between the first optical transmission device and the second optical transmission device, modifies the indicator value based on the span loss, and calculates a deviation amount between the first quality and the modified indicator value; and the estimator estimates the second quality based on the amount of deviation.
12 . An optical transmission system comprising: a first optical transmission device that transmits a first signal light and a second signal light of different wavelengths, both of the first signal light and the second signal light being in actual operation; a second optical transmission device that receives the first signal light and the second signal light, and transmits the first signal light and a first pseudo light having a plurality of wavelengths including the wavelength of the second signal light; a third optical transmission device that receives the first signal light and the first pseudo light from the second optical transmission device; a measurer that measures a first quality of the first pseudo light between the second optical transmission device and the third optical transmission device; and an estimator that estimates a second quality of the first signal light between the first optical transmission device and the third optical transmission device based on the first quality and an indicator value of wavelength dependence in a signal band.
13 . A quality estimation method comprising: estimating a signal quality of a first signal light between a first optical transmission device that transmits a first signal light in actual operation and a first pseudo light having a wavelength different from that of the first signal light and a second optical transmission device that receives the first signal light and the first pseudo light from the first optical transmission device; and estimating a second quality representing a signal quality of the first signal light between the first optical transmission device and the second optical transmission device based on a first quality representing a signal quality based on measurement of the first pseudo light between the first optical transmission device and the second optical transmission device and an indicator value of wavelength dependence in a signal band.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2024-195070, filed on Nov. 7, 2024, the entire contents of which are incorporated herein by reference. FIELD A certain aspect of embodiments described herein relates to an optical transmission system and a quality estimation method. BACKGROUND A submarine optical communication system is known in which terminal stations transmit and receive wavelength multiplexed optical signals through submarine cables. It is also known to provide a transponder in a terminal station (see, for example, International Publication No. 2021/176923). The wavelength-multiplexed optical signal output from the terminal station of a transmission end includes an optical signal (main signal) on which a data addressed to the terminal station of a reception end is superimposed and a dummy light inserted to compensate for the intensity of the wavelength-multiplexed optical signal according to a presence or absence of the optical signal (see, for example, International Publication No. 2020/158190 and US Patent Application Publication No. 2023/0344541). The dummy light includes a plurality of lights having an arbitrary center wavelength and an arbitrary bandwidth. The dummy light source that outputs the dummy light includes, for example, an amplified spontaneous emission (ASE) light source and a wavelength selective switch (WSS) (see, for example, International Publication No. 2021/060124). Other than that, it is also known that an indicator of a quality of a signal transmitted in a wavelength division multiplexing (WDM) optical communication system is an optical signal-to-noise ratio (OSNR) (see, for example, US Patent Application Publication No. 2019/0115976). SUMMARY According to an aspect of the embodiments, there is provided an optical transmission system includes a first optical transmission device that transmits a first signal light in an actual operation and a first pseudo light having a wavelength different from that of the first signal light, a second optical transmission device that receives the first signal light and the first pseudo light from the first optical transmission device, a measurer that measures a first quality of the first pseudo light between the first optical transmission device and the second optical transmission device, and an estimator that estimates a second quality of the first signal light between the first optical transmission device and the second optical transmission device based on the first quality and an indicator value of wavelength dependence in a signal band. According to another aspect of the embodiments, there is provided an optical transmission system includes a first optical transmission device that transmits a first signal light and a second signal light of different wavelengths, both of the first signal light and the second signal light being in actual operation, a second optical transmission device that receives the first signal light and the second signal light, and transmits the first signal light and a first pseudo light having a plurality of wavelengths including the wavelength of the second signal light, a third optical transmission device that receives the first signal light and the first pseudo light from the second optical transmission device, a measurer that measures a first quality of the first pseudo light between the second optical transmission device and the third optical transmission device, and an estimator that estimates a second quality of the first signal light between the first optical transmission device and the third optical transmission device based on the first quality and an indicator value of wavelength dependence in a signal band. The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an example of an optical network. FIG. 2A is an example of a spectrum diagram of the inserted signal light. FIG. 2B is an example of a spectrum diagram of WDM light. FIG. 2C is an example of a spectrum diagram of the branched signal light. FIG. 3 is an example of a circuit configuration of the ROADM. FIG. 4 is an example of a functional configuration of the controller. FIG. 5 is an example of an OSNR database. FIG. 6 is a diagram for explaining an example of correction of the OSNR database. FIG. 7 is an example of a corrected OSNR database. FIG. 8 is a diagram for explaining a case #1 during actual operation of the optical network. FIG. 9 is an example of estimation of the OSNR of signal light in the case #1. FIG. 10 is another example of estimation of the OSNR of the signal light in the case #1. FIG. 11 is a diagra