US 11,942,755 B2
Optical transmission system and filter penalty reduction method
Kohei Saito, Tokyo (JP); Takashi Kotanigawa, Tokyo (JP); and Tsutomu Kubo, Tokyo (JP)
Assigned to Nippon Telegraph and Telephone Corporation, Tokyo (JP)
Appl. No. 16/972,331
Filed by Nippon Telegraph and Telephone Corporation, Tokyo (JP)
PCT Filed May 29, 2019, PCT No. PCT/JP2019/021311
§ 371(c)(1), (2) Date Dec. 4, 2020,
PCT Pub. No. WO2019/253321, PCT Pub. Date Dec. 12, 2019.
Claims priority of application No. 2018-107958 (JP), filed on Jun. 5, 2018.
Prior Publication US 2021/0234617 A1, Jul. 29, 2021
Int. Cl. H01S 3/13 (2006.01); H01S 5/00 (2006.01); H01S 5/02251 (2021.01); H04B 10/079 (2013.01); H04B 10/572 (2013.01); H04B 10/50 (2013.01); H04J 14/02 (2006.01)
CPC H01S 5/0014 (2013.01) [H01S 5/0021 (2013.01); H01S 5/005 (2013.01); H01S 5/0078 (2013.01); H01S 5/02251 (2021.01); H04B 10/0795 (2013.01); H04B 10/07953 (2013.01); H04B 10/0799 (2013.01); H04B 10/572 (2013.01); H04B 10/0793 (2013.01); H04B 10/503 (2013.01); H04J 14/0202 (2013.01)] 10 Claims
OG exemplary drawing
 
1. An optical transmission system comprising a first transponder unit, including one or more processors, on a transmitting side and a second transponder unit, including one or more processors, on a receiving side, configured to perform transmission and reception of an optical signal through an optical transmission line in which an optical filter having a multiplexing/demultiplexing function of the optical signal is interposed, the first transponder unit on the transmitting side and the second transponder unit on the receiving side each including a respective transmission unit and a respective reception unit, the transmission unit of the first transponder unit configured to transmit the optical signal that has been generated by modulating laser light emitted from a laser light source with an electric signal from a communication apparatus to the optical transmission line, the reception unit of the second transponder unit configured to receive the optical signal from the transmission unit of the first transponder unit through the optical transmission line and convert the received optical signal into an electric signal,
wherein the reception unit of the second transponder unit includes a bit error rate (BER) measurement unit, including one or more processors, configured to measure a BER, based on a received signal of the second transponder unit on the receiving side, and feed the measured BER back to the first transponder unit on the transmitting side,
the transmission unit of the first transponder unit includes a control unit, including one or more processors, configured to perform frequency shift control of shifting a center frequency of the laser light emitted from the laser light source in accordance with the fed back BER so that the center frequency approaches a center frequency of the optical signal received in the second transponder unit on the receiving side, and
the control unit is configured to perform the frequency shift control so that a value of the fed back BER is minimized, wherein minimizing the value of the fed back BER comprises repeatedly shifting the center frequency of the laser light and measuring and recording the corresponding feedback BER until a minimal fed back BER is reached.