Wavelength division multiplexing optical transmission system and transmission method
First Claim
1. A wavelength division multiplexing (WDM) optical transmission system comprising:
- an optical transmitting section having an optical transmitter that generates N wave (wherein N is an integer of 2 or greater) optical signals with an optical frequency spacing Δ
f [Hz] and modulated by a modulation bit rate B [bit/s] (wherein B/Δ
f≦
1 [bit/s/Hz]) using a modulation device, and having a coupler that couples the optical signals;
an optical receiving section provided with an optical discrete Fourier transform (DFT) circuit that performs a DFT on wavelength division multiplexed signals transmitted from the optical transmitting section at a sampling frequency Δ
f [Hz] that is equal to the optical frequency spacing and separates the wavelength division multiplexed signals into signal components of each optical frequency; and
a bit phase adjustor that makes bit phases of respective wavelength division multiplexed signals synchronous at an input terminal of the optical DFT circuit.
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Accused Products
Abstract
There is provided a WDM optical transmission system and transmission method that have excellent spectral efficiency. The WDM optical transmission system is provided with: an optical transmitting section having an optical transmitter that generates N wave (wherein N is an integer of 2 or greater) optical signals with an optical frequency spacing Δf [Hz] and modulated by a modulation bit rate B [bit/s] (wherein B/Δf≦1 [bit/s/Hz]) using a modulation device, and having a coupler that couples the optical signals; an optical receiving section provided with an optical DFT circuit of a sampling frequency Δf [Hz] that is equal to the optical frequency spacing; and a bit phase adjustor that makes bit phases of respective wavelength division multiplexed signals synchronous at an input of the optical DFT circuit.
22 Citations
19 Claims
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1. A wavelength division multiplexing (WDM) optical transmission system comprising:
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an optical transmitting section having an optical transmitter that generates N wave (wherein N is an integer of 2 or greater) optical signals with an optical frequency spacing Δ
f [Hz] and modulated by a modulation bit rate B [bit/s] (wherein B/Δ
f≦
1 [bit/s/Hz]) using a modulation device, and having a coupler that couples the optical signals;an optical receiving section provided with an optical discrete Fourier transform (DFT) circuit that performs a DFT on wavelength division multiplexed signals transmitted from the optical transmitting section at a sampling frequency Δ
f [Hz] that is equal to the optical frequency spacing and separates the wavelength division multiplexed signals into signal components of each optical frequency; anda bit phase adjustor that makes bit phases of respective wavelength division multiplexed signals synchronous at an input terminal of the optical DFT circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A WDM optical transmission system comprising:
an optical transmitting section that generates N wave (wherein N is an integer of 2 or greater) optical signals with an optical frequency spacing Δ
f [Hz] and modulated by a modulation bit rate B [bit/s] (wherein B/Δ
f≦
1 [bit/s/Hz]) using a modulation device, and couples the optical signals;an optical receiving section provided with; an asymmetrical Mach-Zehnder interference device that takes transmitted signals from the optical transmitting section as an input and whose optical path length difference is c/(2ncΔ
f) (wherein c is the speed of light, and nc is an effective refractive index of an optical line);a wavelength filter that selects and transmits a desired wavelength from output signals of the asymmetrical Mach-Zehnder interference device; and a time gate that extracts signals in bit units of a time from 1/(2Δ
f) [s] to T[s] (wherein T is the period of one bit) from signals output by the wavelength filter; anda bit phase adjustor that makes bit phases of respective wavelength division multiplexed signals synchronous at an input terminal of the asymmetrical Mach-Zehnder interference device. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A WDM optical transmission method comprising the steps of:
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N wave (wherein N is an integer of 2 or greater) optical signals with an optical frequency spacing Δ
f [Hz] and modulated by a modulation bit rate B [bit/s] (wherein B/Δ
f≦
1 [bit/s/Hz]) using a modulation device are generated, and the optical signals are coupled and transmitted; andthe transmitted optical signals are received using an optical DFT circuit that performs a DFT at a sampling frequency Δ
f [Hz] that is equal to the optical frequency spacing and separates the transmitted optical signals into signal components of each optical frequency, andbit phases are adjusted such that bit phases of respective wavelength division multiplexed signals at an input terminal of the optical DFT circuit are synchronized.
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19. A WDM optical transmission method comprising the steps of:
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N wave (wherein N is an integer of 2 or greater) optical signals with an optical frequency spacing Δ
f [Hz] and modulated by a modulation bit rate B [bit/s] (wherein B/Δ
f≦
1 [bit/s/Hz]) using a modulation device are generated, and the optical signals are coupled and transmitted;bit phase adjustment is performed such that the bit phases of the respective transmitted wavelength division multiplexed signals are synchronized, and the transmitted signals are input into an asymmetrical Mach-Zehnder interference device whose optical path length difference is c/(2ncΔ
f) (wherein c is the speed of light, and nc is an effective refractive index of an optical line);a desired wavelength is selected from an output of the asymmetrical Mach-Zehnder interference device; and signals of a time from 1/(2Δ
f) [s] to T[s] (wherein T is the period of one bit) are extracted from the selected signals in bit units and the extracted signals are output.
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Specification