Optical transmission apparatus, optical transmission system, and optical terminal station

• US 20020101633A1
• Filed: 12/31/2001
• Published: 08/01/2002
• Est. Priority Date: 04/02/1998
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Nakazawa, Tadao, Miyata, Hideyuki, Onaka, Hiroshi, Kai, Yutaka, Chikama, Terumi, Otsuka, Kazue
• Granted Patent: US 6,583,900 B2
• Time in Patent Office: Days
• US Class Current: 398/59
• CPC Class Codes: H04J 14/0204 Broadcast and select arrangements, e.g. with an optical splitter at the input before adding or dropping
• CPC Class Codes: H04J 14/0205 Select and combine arrangements, e.g. with an optical combiner at the output after adding or dropping
• CPC Class Codes: H04J 14/0206 Express channels arrangements
• CPC Class Codes: H04J 14/0209 Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers
• CPC Class Codes: H04J 14/021 Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM]
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0213 Groups of channels or wave bands arrangements
• CPC Class Codes: H04J 14/0219 Modular or upgradable architectures
• CPC Class Codes: H04J 14/0283 WDM ring architectures
• CPC Class Codes: H04J 14/0289 Optical multiplex section protection
• CPC Class Codes: H04J 14/0291 Shared protection at the optical multiplex section (1:1, n:m)
• CPC Class Codes: H04J 14/0294 Dedicated protection at the optical channel (1+1)
• CPC Class Codes: H04J 14/0297 Optical equipment protection

Abstract

In an OADM system, an OADM device includes an AOTF. The AOTF can select an optional wavelength by changing the frequency of an RF signal to be applied. An optical signal having a specified wavelength can be dropped from a wavelength-multiplexed optical signal input from an input terminal, or a wavelength-multiplexed optical signal input from an add port can be multiplexed with a through optical signal. However, considering the increase in coherent cross talk, the AOTF should be exclusively used for dropping in an actual device configuration. Otherwise, a drop optical signal is branched by an optical coupler with the wavelength selected by a tributary station. Thus, the wavelength selected by the tributary station can be extracted by the AOTF from the through optical signal.

Claims

1. A transmission ring system, transmitting a plurality of wavelength channels, comprising:

a first transmission line on which a first portion of the wavelength channels are used for current use, and a second portion of the wavelength channels are used for standby use, wherein an optical signal is transmitted in a first direction via the first transmission line;

a second transmission line on which the second portion of the wavelength channels are used for current use, and the first portion of the wavelength channels are used for standby use, wherein an optical signal is transmitted in a second direction, opposite the first direction, via the second transmission line; and

a plurality of nodes, each of which accommodates both the first transmission line and the said second transmission line.

2. A node used for a transmission ring system transmitting a plurality of wavelength channels, comprising:

a first unit to process optical signals carried by a first portion of the wavelength channels which are used for current use on a first transmission line, wherein said optical signals are transmitted in a first direction via the first transmission line;

a second unit to process optical signals carried by a second portion of the wavelength channels used for standby use on the first transmission line, and used for current use on a second transmission line, wherein the optical signals are transmitted in a second direction, opposite to the first direction, via the second transmission line; and

a loop back configuration to switch the transmission line from which the first and second units process optical signals, from the first transmission line to the second transmission line or from the second transmission line to the first transmission line.

3. A transmission ring system transmitting a plurality of wavelength channels, comprising:

a first bi-directional transmission line on which some of the wavelength channels are transmitted in a first direction, and the others of the wavelength channels are transmitted in a second direction, the first bi-directional transmission line being used for current use;

a second bi-directional transmission line on which some of the wavelength channels transmitted in the second direction on the first bi-directional transmission line are transmitted in the first direction, and the others of the wavelength channels transmitted in the first direction on the first bi-directional transmission line are transmitted in the second direction, the second bi-directional transmission line being used for standby use; and

a plurality of nodes, each of which accommodates both the first bi-directional transmission line and the second bi-directional transmission line.

4. A node used for a transmission ring system which transmits optical signals by a plurality of wavelength channels, comprising:

a first unit to process optical signals carried by the wavelength channels on a first bi-directional transmission line, wherein some of the wavelength channels are transmitted in a first direction and the others of the wavelength channels are transmitted in a second direction, the first unit being used as a working unit;

a second unit to process optical signals carried by the wavelength channels on a second bi-directional transmission line, wherein some of the wavelength channels transmitted in the second direction on the first bi-directional transmission line are transmitted in the first direction on the second bi-directional transmission line, and the others of the wavelength channels transmitted in the first direction on the first bi-directional transmission line are transmitted in the second direction on the second bi-directional transmission line, the second unit being used as a protection unit; and

loop back means for switching from the first bi-directional transmission line to the second bi-directional transmission line or from the second bi-directional transmission line to the first bi-directional transmission line.

5. A transmission ring system transmitting a plurality of wavelength channels, comprising:

a first bi-directional transmission line on which a first portion of the wavelength channels are transmitted in a first direction, and a second portion of the wavelength channels are transmitted in a second direction, the first bi-directional transmission line being used for current use;

a second bi-directional transmission line on which the second portion of the wavelength channels are transmitted in the first direction, and the first portion of the wavelength channels are transmitted in the second direction, the second bi-directional transmission line being used for standby use; and

a plurality of nodes, each of which accommodates both the first bi-directional transmission line and the second bi-directional transmission line.

6. A node used for a transmission ring system which transmits optical signals by a plurality of wavelength channels, comprising:

a first unit to process optical signals carried by the wavelength channels on a first bi-directional transmission line, wherein a first portion of the wavelength channels are transmitted in a first direction and a second portion of the wavelength channels are transmitted in a second direction opposite to the first direction on the first bi-directional transmission line, the first unit being used as a working unit;

a second unit to process optical signals carried by the wavelength channels on a second bi-directional transmission line, wherein the second portion of the wavelength channels are transmitted in the first direction and the second portion of the wavelength channels are transmitted in the second direction on the second bi-directional transmission line, the second unit being used as a protection unit; and

a loop back configuration to switch the transmission line from which the first and second units process optical signals, from the first bi-directional transmission line to the second bi-directional transmission line or from the second bi-directional transmission line to the first bi-directional transmission line.