| US 7,555,215 B2 | ||
| Optical wavelength division multiplexing access system | ||
| Hirotaka Nakamura, Narashino (Japan); Junichi Kani, Narashino (Japan); Hiroo Suzuki, Yokohama (Japan); Mitsuhiro Teshima, Yokosuka (Japan); Ukyo Yamaguchi, Yachiyo (Japan); Hidetaka Onishi, Chiba (Japan); and Katsumi Iwatsuki, Yokohama (Japan) | ||
| Assigned to Nippon Telegraph and Telephone Corporation, Tokyo (Japan) | ||
| Appl. No. 10/535,526 PCT Filed May 28, 2004, PCT No. PCT/JP2004/007773 § 371(c)(1), (2), (4) Date May 18, 2005, PCT Pub. No. WO2004/107626, PCT Pub. Date Dec. 09, 2004. |
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| Claims priority of application No. 2003-151539 (JP), filed on May 28, 2003. | ||
| Prior Publication US 2006/0062576 A1, Mar. 23, 2006 | ||
| Int. Cl. H04J 14/00 (2006.01); H04B 10/08 (2006.01) | ||
| U.S. Cl. 398—72 [398/67; 398/68; 398/70; 398/71; 398/5; 398/7; 398/20; 398/21; 398/30; 398/31; 398/35; 398/92] | 27 Claims |
| 1. An optical wavelength division multiplexing access system, comprising a center node (OSU) and n optical network units (ONUs)
arranged by using a W-MULDEM unit, a multiplexing section between the OSU and the W-MULDEM unit established by extending a
current-use optical fiber and a redundant optical fiber and access sections between the W-MULDEM unit and the individual ONUs
established by the extension of optical fibers, wherein downstream optical signals from the OSU to the ONUs and upstream optical
signals from the ONUs to the OSU are multiplexed using wavelengths that are allocated to individual ONUs and the resultant
signals are transmitted across the multiplexing section, and wherein the W-MULDEM unit performs wavelength multiplexing or
wavelength demultiplexing for the upstream or downstream optical signals to provide bidirectional transmission,
the OSU includes:
a transmission device for multiplexing downstream optical signals having wavelengths λd1 to λdn that correspond to the ONUs and transmitted to the ONUs along the current-use optical fiber, for multiplexing downstream
optical signals having wavelengths λd1+Δλ to λdn+Δλ that correspond to the ONUs and transmitted to the ONUs along the redundant optical fiber, and for selecting
either the current-use optical fiber or the redundant optical fiber for transmission, and
a reception device for receiving upstream optical signals having wavelengths λu1 to λun along the current-use optical fiber or for receiving upstream optical signals having wavelengths λu1+Δλ to λun+Δλ along the redundant optical fiber;
the individual ONUs receive corresponding downstream optical signals having wavelengths λd1 to λdn or corresponding downstream optical signals having wavelengths λd1+Δλ to λdn+Δλ, which are received along the optical fibers extended across the access sections, the individual ONUs transmit,
to the optical fibers extended across the access sections, corresponding upstream optical signals that have wavelengths λu1 to λun and transmitted along the current-use optical fiber extended across the multiplexing section, or corresponding upstream
optical signals that have wavelengths λu1+Δλ to λun+Δλ and transmitted along the redundant optical fiber;
the W-MULDEM unit includes an array waveguide diffraction grating (AWG) having two ports, respectively connected to the current-use
optical fiber and the redundant optical fiber, and n ports, connected to optical fibers corresponding to the ONUs;
the W-MULDEM unit demultiplexes to the ports corresponding to the ONUs the downstream optical signals that have wavelengths
λd1 to λdn and are received along the current-use optical fiber, or the downstream optical signals that have wavelengths λd1+Δλ to λdn+Δλ and are received along the redundant optical fiber, or multiplexes, to the port corresponding to the current-use
optical fiber or the redundant optical fiber, the upstream optical signals that have wavelengths λu1 to λun or wavelengths λu1+Δλ to λun+Δλ and that are received along the optical fibers corresponding to the ONUs;
a wavelength difference between the downstream optical signal and the upstream optical signal corresponding to each of the
ONUs is integer times a free spectrum range (FSR) of the AWG;
the two ports of the AWG are provided at locations consonant with a wavelength difference (Δλ) between optical signals transmitted
along the current-use optical fiber and optical signals transmitted along the redundant optical fiber corresponding to each
of the ONUs; and
wherein the transmission device includes:
a switching device for changing from a current-use optical fiber to a redundant optical fiber;
a supervisory light source for outputting current-use fiber supervisory light and reserve fiber supervisory light having wavelengths
λs0 and λs1 that differ from the wavelengths of the upstream optical signals and the downstream optical signals;
a supervisory control unit, for detecting the supervisory light having wavelengths λs0 and λs1 that is received along the current-use optical fiber and the redundant optical fiber, and outputting a selection signal to
the switching device to change from the current-use optical fiber to the redundant optical fiber;
a multiplexing unit, for multiplexing the current-use fiber supervisory light having wavelength λs0 and an optical signal transmitted along the current-use optical fiber;
a demultiplexing unit, for demultiplexing the current-use fiber supervisory light having wavelength λs0 from an optical signal transmitted along the current-use optical fiber;
a multiplexing unit, for multiplexing the reserve fiber supervisory light having wavelength λs1 and an optical signal transmitted along the redundant optical fiber; and
a demultiplexing unit, for demultiplexing the reserve fiber supervisory light having wavelength λs1 from an optical signal transmitted along the redundant optical fiber.
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