Node apparatus, optical wavelength division multiplexing network, and system switching method

• US 7,433,594 B2
• Filed: 10/12/2006
• Issued: 10/07/2008
• Est. Priority Date: 02/21/2000
• Status: Expired due to Fees

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Iwatsuki, Katsumi, Obara, Hitoshi, Takachio, Noboru
• Primary Examiner(s): Vanderpuye; Kenneth
• Assistant Examiner(s): Liu; Li
• Application Number:
  US11/580,568
• Publication Number:
  US 20070031146A1
• Time in Patent Office: 726 Days
• Field of Search: 398/1, 398/4, 398/9, 398/30, 398 43- 79, 398/83, 398/115, 398/119, 398/5
• US Class Current: 398/4
• CPC Class Codes: H04B 10/271 Combination of different networks, e.g. star and ring configuration in the same network or two ring networks interconnected
• CPC Class Codes: H04B 10/272 Star-type networks or tree-type networks
• CPC Class Codes: H04B 10/2755 Ring-type networks with a headend
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/0282 WDM tree architectures
• CPC Class Codes: H04J 14/0283 WDM ring architectures
• CPC Class Codes: H04J 14/0286 WDM hierarchical architectures
• CPC Class Codes: H04J 14/029 Dedicated protection at the optical multiplex section (1+1)
• CPC Class Codes: H04J 14/0305 in end terminals
• CPC Class Codes: H04Q 11/0062 Network aspects
• CPC Class Codes: H04Q 11/0067 Provisions for optical access or distribution networks, e.g. Gigabit Ethernet Passive Optical Network (GE-PON), ATM-based Passive Optical Network (A-PON), PON-Ring
• CPC Class Codes: H04Q 2011/0086 Network resource allocation, dimensioning or optimisation

Abstract

An optical wavelength division multiplexing network has a multi-level structure where a plurality of optical network units (ONUs) are connected to a lowest-level network. A node apparatus connected to networks other than the lowest-level network includes (a) passive optical components to branch optical signals from a higher-level network to a lower-level network, and couple optical signals from the lower-level network to the higher-level network, and (b) optical amplifiers for the optical signals. A node apparatus connected to the lowest-level network includes (a) an optical multiplexer/de-multiplexer to de-multiplex optical signals from the higher-level network, selectively output an optical signal to each ONU, and multiplex wave-length specific optical signals from the ONUs into a multiplexed optical signal, and (b) optical amplifiers for the optical signals. The node apparatuses provide an optical communication path between the higher-level network and the lower-level (or lowest-level) network without converting the optical signals into electrical signals.

Claims

1. A node apparatus in an optical wavelength division multiplexing network having a multi-level structure, said node apparatus being connected to a lowest level network and a network higher than the lowest level network (hereinafter referred to as a “

higher level network”

), the higher level network including a bidirectional primary fiber path and a bidirectional protection fiber path, the lowest level network including a plurality of optical network units (ONUs) connected thereto, each ONU being allocated with a respective wavelength and capable of de-multiplexing, said node apparatus comprising;

a first passive optical component configured to receive and branch optical signals from the bidirectional primary fiber path, and couple optical signals received from the lowest level network to the bidirectional primary fiber path;

a second passive optical component configured to receive and branch optical signals from the bidirectional protection fiber path, and couple optical signals received from the lowest level network to the bidirectional protection fiber path;

an optical switch configured to select and output optical signals received from the bidirectional primary fiber path if the optical signals are being input from the bidirectional primary fiber path, and select and output optical signals received from the bidirectional protection fiber path if severance of the optical signals is detected in input from the bidirectional primary fiber path;

an optical divider configured to divide optical signals received from the ONUs into a plurality of directions, the divided optical signals being coupled to the first and second passive optical components;

bidirectional optical amplifiers configured to amplify the optical signals input to and output from said first and second passive optical components;

an optical star coupler connected to the ONUs; and

an optical circulator provided between said optical switch and said optical star coupler, said optical circulator being coupled to said optical divider,

wherein said node apparatus provides an optical communication path between the higher level network and the lowest level network without converting the optical signals into electrical signals.

2. A node apparatus in an optical wavelength division multiplexing network having a multi-level structure, said node apparatus being connected to a highest level network, the highest level network including a primary optical fiber path and a protection optical fiber path, said node apparatus being a multiplexing destination of traffic from lower level networks, said node apparatus comprising:

a first optical de-multiplexer configured to receive optical signals from the primary optical fiber path and de-multiplex the received optical signals into first de-multiplexed optical signals having respective wavelengths;

a second optical de-multiplexer configured to receive optical signals from the protection optical fiber path and de-multiplex the received optical signals into second de-multiplexed optical signals having respective wavelengths;

a signal selection circuit coupled to said first and second optical de-multiplexers, said signal selection circuit configured to select, for each wavelength, either one of the first or second de-multiplexed optical signal based on severance of received optical signals, and output the selected de-multiplexed optical signals as de-multiplexed electrical signals;

an signal processing circuit coupled to said signal selection circuit, said signal processing circuit configured to receive and electrically process the de-multiplexed electrical signals, and output processed de-multiplexed electrical signals as processed de-multiplexed optical signals in two directions;

a first optical multiplexer configured to receive and multiplex the processed de-multiplexed optical signals in a first direction and output to the primary optical fiber path; and

a second optical multiplexer configured to receive and multiplex the processed de-multiplexed optical signals in a second direction and output the protection optical fiber path.

3. The node apparatus of claim 2, wherein said signal selection circuit comprising:

a plurality of first optical receivers coupled to said first de-multiplexer, said first optical receivers configured to convert the first de-multiplexed optical signals into first de-multiplexed electrical signals;

a plurality of second optical receivers coupled to said second de-multiplexers, said second optical receivers configured to convert the second de-multiplexed optical signals into second de-multiplexed electrical signals; and

a plurality of selectors coupled to said first and second optical receivers, said selectors configured to selectively output either one of the first or second de-multiplexed electrical signals to said signal processing circuit.

4. The node apparatus of claim 2, wherein said signal processing circuit comprising:

a signal termination section configured to perform predetermined electrical processing and output processed electrical signals in two directions; and

a plurality of optical senders coupled to said signal termination section, configured to convert the processed electrical signals into corresponding optical signals.

5. The node apparatus of claim 2, wherein said signal selection circuit comprising:

a plurality of optical switches coupled to said first and second de-multiplexers, said optical switches configured to selectively output either one of the first or second de-multiplexed optical signals; and

a plurality of optical receivers each coupled to a corresponding one of said optical switches, said optical receivers configured to convert the selected de-multiplexed optical signals into a corresponding electrical signals.

6. The node apparatus of claim 2, wherein said signal processing circuit comprising:

a signal termination section configured to perform predetermined electrical processing;

a plurality of optical senders coupled to said signal termination section, configured to convert processed electrical signals into corresponding processed optical signals; and

a plurality of optical dividers configured to divide the processed optical signals into two directions.