Patent ID: 11936422
Assignee: NEC CORPORATION
Field: Telecommunications (Electrical engineering)
Classification: CPC H | IPC H

Claim 5:
6. A submarine apparatus comprising:
an optical branching unit inserted into an optical fiber included in a submarine optical cable and configured to branch a part of a signal light including a reference signal light transmitted by the optical fiber; and
a spectrum monitoring apparatus configured to monitor a spectrum of the signal light including the reference signal light branched by the optical branching unit, wherein
the spectrum monitoring apparatus comprises:
a variable optical bandpass filter configured to allow a signal light of a specified wavelength band in the signal light including the reference signal light to pass through;
a light receiving unit configured to receive the signal light that has passed through the variable optical bandpass filter and output a level signal indicating a level of the received signal light; and

a control unit configured to instruct a wavelength band that is allowed to pass through the variable optical bandpass filter by referring to a wavelength table held in advance, and obtain a spectrum of the signal light having passed through the variable optical bandpass filter by using the wavelength table and the level signal, wherein
the control unit:
detects a wavelength drift between the center wavelength of the wavelength band instructed to the variable optical bandpass filter to allow the reference signal light to pass through and a center wavelength of a peak corresponding to the reference signal light in the spectrum; and
updates the wavelength table to correct the detected wavelength drift.