US 12,034,487 B2
Optical transmission system
Taiji Sakamoto, Musashino (JP); Masaki Wada, Musashino (JP); Takashi Yamamoto, Musashino (JP); and Kazuhide Nakajima, Musashino (JP)
Assigned to NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
Appl. No. 17/633,902
Filed by NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
PCT Filed Aug. 23, 2019, PCT No. PCT/JP2019/033162
§ 371(c)(1), (2) Date Feb. 8, 2022,
PCT Pub. No. WO2021/038661, PCT Pub. Date Mar. 4, 2021.
Prior Publication US 2022/0294537 A1, Sep. 15, 2022
Int. Cl. H04B 10/61 (2013.01); H04B 10/2575 (2013.01); H04B 10/2581 (2013.01)
CPC H04B 10/614 (2013.01) [H04B 10/25753 (2013.01); H04B 10/2581 (2013.01)] 4 Claims
OG exemplary drawing
 
1. An optical transmission system, comprising:
an optical fiber configured for spatial multiplexing with the number of spatial modes being L (L is an integer of 2 or more);
an optical multiplexer being connected to one end of the optical fiber, and configured to input signal beams of light from M transmitters (M is a natural number of L or less) to the optical fiber and cause each of the input signal beams of light to be propagated for each of the spatial modes of the optical fiber;
an optical demultiplexer being connected to another end of the optical fiber, and configured to demultiplex a propagated beam of light caused to be propagated through the optical fiber for each of the spatial modes of the optical fiber;
N (N=L) receivers configured to each receive a demultiplexed beam of light obtained by demultiplexing the propagated beam of light by the optical demultiplexer;
an N×M multiple-input multiple-output (MIMO) equalizer configured to receive N received signals output from the N receivers and output M demodulated signals;
a controller configured to instruct the optical multiplexer to change the number M of the signal beams of light input to the optical fiber; and
a measuring instrument configured to measure a signal quality of a demodulated signal of the M demodulated signals and notify the controller of the number M of the signal beams of light so that the signal quality exceeds a threshold value.