OPTICAL TRANSMITTER, OPTICAL TRANSCEIVER USING OPTICAL TRANSMITTER, AND WAVELENGTH CONTROL METHOD

1 . An optical transmitter comprising:

a frequency comb light source;

a demultiplexer configured to demultiplex light output from the frequency comb light source into n channels (n is an integer of 2 or greater) at a wavelength interval Δλ; and

n filters respectively connected to n output ports of the demultiplexer, the n filters being configured to reduce a high-order spectral component for each wavelength.

2 . The optical transmitter as claimed in claim 1 , further comprising a controller configured to control a peak wavelength of a transmission spectrum of each of the n filters.

3 . The optical transmitter as claimed in claim 2 , wherein each of the n filters includes one or more asymmetric Mach-Zehnder interferometers connected in series.

4 . The optical transmitter as claimed in claim 3 , wherein a k-th asymmetric Mach-Zehnder interferometer (k is an integer of 1 or greater) among the one or more asymmetric Mach-Zehnder interferometers has a transmission characteristic having a period of 2 k−1 ×2n×Δλ.

5 . The optical transmitter as claimed in claim 2 , wherein each of the n filters includes a resonator configured to resonate with a corresponding channel wavelength.

6 . The optical transmitter as claimed in claim 5 , wherein a free spectral range of the resonator is greater than n×Δλ.

7 . The optical transmitter as claimed in claim 1 ,

wherein the demultiplexer includes 2 L −1 unit circuits connected in a tree-shaped branching structure in L stages (L is an integer of 1 or greater),

wherein each of the 2 L −1 unit circuits has one input port and two outputs ports, and

wherein the n filters are respectively connected to output ports of a unit circuit at an L-th stage among the L stages.

8 . The optical transmitter as claimed in claim 7 ,

wherein each of the 2 L −1 unit circuits includes a first asymmetric Mach-Zehnder interferometer, a second asymmetric Mach-Zehnder interferometer, and a third asymmetric Mach-Zehnder interferometer having an identical arm length difference, and

wherein an arm length difference of a unit circuit at the L-th stage is ½ of an arm length difference of a unit circuit at an (L−1)-th stage among the L stages.

9 . The optical transmitter as claimed in claim 1 , further comprising:

n optical modulators provided corresponding to the n filters; and

a multiplexer configured to multiplex output light of the n optical modulators.

10 . An optical transceiver comprising:

the optical transmitter as claimed in claim 1 ; and

an optical receiver;

wherein the optical receiver demultiplexes received a wavelength division multiplexing signal into optical signals of respective wavelengths, and detects the demultiplexed optical signals of the respective wavelengths by using a portion of light transmitted through the n filters of the optical transmitter as local oscillation light.

11 . A wavelength control method comprising:

demultiplexing, by a demultiplexer, light output from a frequency comb light source into n channels (n is an integer of 2 or greater) at a wavelength interval Δλ; and

controlling a filter to bring a peak of a transmission spectrum of the filter close to a wavelength appearing at a corresponding output port of the demultiplexer to reduce a high-order spectral component for each wavelength, the filter being provided to each of n output ports of the demultiplexer.