Abstract:
A grooming apparatus for an optical communication network is disclosed. The apparatus mainly includes a first photoelectric integration unit and an electrical-layer grooming unit. The first photoelectric integration unit includes a wavelength division multiplexing/demultiplexing unit and a photo-electric/electric-photo conversion unit. The wavelength division demultiplexing unit is configured to demultiplex a multi-wavelength optical signal into single-wavelength optical signals. The photo-electric conversion unit is configured to convert the single-wavelength optical signals to single-wavelength electrical signals. The electrical-layer grooming unit is configured to groom the single-wavelength electrical signals. The present invention overcomes the fatal defect of light dispersion, light power estimation, light power adjustment, OSNR limitation for a conventional OADM/ROADM system. Also, the flexibility of the electrical-layer grooming eliminates the wavelength broadcast and multicast issue. The processing of the electrical layer also addresses the wavelength monitoring issue and the wavelength conflict issue.

Description:
CROSS REFERENCE 
     The application is a continuation of International Application No. PCT/CN2008/070023, filed on Jan. 4, 2008, which claims priority to Chinese Patent Application No. 200710087515.x, filed on Mar. 16, 2007 with the State Intellectual Property Office of the People&#39;s Republic of China, entitled “GROOMING METHOD AND APPARATUS FOR OPTICAL COMMUNICATION NETWORK”, the entire contents of all of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to grooming technique in communication field, and more specifically to grooming apparatus and method for optical communication network. 
     BACKGROUND 
     With the rapid development of packet service, the design of future communication network is focusing on optimizing packet service, especially IP service. Therefore, it is vital to enhance service grooming capability and improve the efficiency of service transmission. Currently, a grooming method mainly includes the following electrical cross connection or optical cross connection on a wavelength level basis, such as Reconfiguration Optical Add/Drop Multiplexing (ROADM), can selectively transfer upstream/downstream local service and carry out transmission based on a certain wavelength while transmission of other wavelengths is not affected. 
     The existing ROADM includes ROADM based on Wavelength Selected Switch (WSS). The structure of such ROADM is illustrated in  FIG. 1 .  FIG. 1  illustrates a 4 dimensional ROADM system constituted by 8 WSS devices, with two loops of services invoking each other. There are various approaches to implement WSS. The most popular one is Micro-Electro Mechanical System (MEMS) technique. The WSS-based ROADM operates in the following way. A multi-wavelength optical signal is de-multiplexed by a grating device into a plurality of optical signals with different single wavelengths. After optical signals with different single wavelengths are amplified and dispersion-compensated, they were focused on different MEMS lenses. By controlling the reflection angle of the MEMS lenses, optical signals with different single wavelengths can be reflected at different output ports. Each output port employs the grating device to multiplex these single-wavelength optical signals into a multi-wavelength optical signal. Since each MEMS device is controlled independently, configuring an optical signal with arbitrary wavelength to an arbitrary output port can be achieved. Moreover, each output port of WSS may also be able to transfer upstream/downstream local services. 
     Inventors of the present invention discover that the existing ROADM has the following defects. The issues of light dispersion and light power loss cannot be addressed thoroughly. Especially, for a network with multi-dimensional nodes, the light dispersion and light power loss problem is particularly severe, and the light noise accumulation is also considerable. Moreover, the existing ROADM cannot adequately monitor the light signal-to-noise ratio, which affects the management of light signal-to-noise ratio. The existing ROADM also fails to monitor wavelength in real time, which affects the monitoring of optical wavelength from port to port. Also, the existing ROADM cannot address the wavelength conflicts and does not support broadcast or multicast of the service. Further, the existing ROADM employs optical devices which are rather expensive and may not be commercialized at present. 
     SUMMARY 
     Grooming apparatuses and methods for optical communication network are provided according to an embodiment of the present invention. The apparatuses and methods provide solution to the light noise accumulation problem, eliminate optical wavelength conflicts, and support broadcast and multicast service. 
     To solve the foregoing problem, technical solutions are presented below to achieve the objective of the present invention. 
     A grooming apparatus for an optical communication network includes a first photoelectric integration unit and an electrical-layer grooming unit. The first photoelectric integration unit includes a wavelength division demultiplexing unit and a photo-electric conversion unit. 
     The wavelength division demultiplexing unit is configured to demultiplex a received multi-wavelength optical signal into single-wavelength optical signals. 
     The photo-electric conversion unit is configured to perform a photo-electric conversion on the single-wavelength optical signals and generate single-wavelength electrical signals. 
     The electrical-layer grooming unit is configured to groom the single-wavelength electrical signal and output the groomed electrical signals. 
     A grooming apparatus for an optical communication network includes: 
     a mapping unit, configured to map service data into a unified mapped container signal; 
     an electrical-layer grooming unit, configured to groom the unified mapped container signal; 
     an electric-photo conversion unit, configured to perform an electric-photo conversion on the unified mapped container signal output from the electrical-layer grooming unit and generate single-wavelength optical signals; and 
     a wavelength division multiplexing unit, configured to multiplex single-wavelength optical signals into a multi-wavelength optical signal and output the multi-wavelength optical signal. 
     A grooming method for an optical communication network includes: 
     demultiplexing a received multi-wavelength optical signal into single-wavelength optical signals; 
     performing an photo-electric conversion on the single wavelength optical signals with and generating single-wavelength electrical signals; and 
     grooming and outputting the single-wavelength electrical signals. 
     A grooming method for an optical communication network includes: 
     mapping service data into a unified mapped container signal; 
     grooming the unified mapped container signal; 
     performing an electric-photo conversion on the groomed unified container signal and generating a single-wavelength optical signal; and 
     multiplexing the single-wavelength optical signals into a multi-wavelength optical signal and outputting the multi-wavelength optical signal. 
     As can be seen from the above technical solutions, embodiments of the present invention perform a photo-electric conversion on optical signals and groom the electrical signal. Photo-electric conversion is performed in the optical network so that the light noise accumulation is eliminated, addressing the problem of the restricted grooming of light signal-to-noise ratio. An electrical-layer grooming unit is also employed to output the single-wavelength electrical signals. Due to the characteristics of the electrical-layer grooming unit, the present invention is able to address the optical wavelength conflict issue and can support broadcast and multicast services. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an architecture of ROADM in the prior art; 
         FIG. 2  is a block diagram of a grooming apparatus in an optical communication network according to a first embodiment of the present invention; 
         FIG. 3  is a block diagram of a grooming apparatus in an optical communication network according to a second embodiment of the present invention; 
         FIG. 4  is a block diagram of a grooming apparatus in an optical communication network according to a third embodiment of the present invention; 
         FIG. 5  is a block diagram of a grooming apparatus in an optical communication network according to a fourth embodiment of the present invention; 
         FIG. 6  is a block diagram of a grooming apparatus in an optical communication network according to a fifth embodiment of the present invention; 
         FIG. 7  is a block diagram of a grooming apparatus in an optical communication network according to a sixth embodiment of the present invention; 
         FIG. 8  is a block diagram of a grooming apparatus in an optical communication network according to a seventh embodiment of the present invention; 
         FIG. 9  is a block diagram of a grooming apparatus in an optical communication network according to an eighth embodiment of the present invention; and 
         FIG. 10  is a block diagram of a grooming apparatus in an optical communication network according to a ninth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Detailed description on various embodiments of the present invention is given below in connection with the accompany drawings. 
       FIG. 2  is a block diagram of a grooming apparatus in an optical communication network according to a first embodiment of the present invention. The apparatus is used to groom optical wavelength. The apparatus includes a first photoelectric integration unit  201 , an electrical-layer demultiplexing unit  202 , an electrical-layer grooming unit  203 , an electrical-layer multiplexing unit  204 , and a second photo-electric integration unit  205 . The first photo-electric integration unit  201  includes a wavelength division demultiplexing unit  2011 , photo-electric conversion unit  2012 . The second photoelectric integration unit  205  includes an electric-photo conversion unit  2052  and a wavelength division multiplexing unit  2051 . 
     A multi-wavelength optical signal is decomposed by the wavelength division demultiplexing unit  2011  into a plurality of single-wavelength optical signals. The single-wavelength optical signals undergo a photo-electric convention by a photo-electric conversion unit  2012  and become single-wavelength electrical signals. The single-wavelength electrical signals are electrical signals converted from a single-wavelength optical signal. The first photoelectric integration unit  201  implements amplification, rectification, and re-timing, which can be configured to recover the single-wavelength optical signals, compensate the dispersion occurred in the Wavelength Division Multiplexing (WDM) system and compensate the light power loss. The electrical-layer demultiplexing unit  202  is configured to de-multiplex the single-wavelength electrical signals and output a unified mapped container signal. The unified mapped container signal may be a Virtual Container (VC) or an Optical Channel Data Unit (ODU). 
     The electrical-layer grooming unit  203  grooms the unified mapped container signal and outputs this signal to the electrical-layer multiplexing unit  204 . The electrical-layer grooming unit  203  may employ an electrical-layer grooming matrix to groom the electrical-layer signal. The electrical-layer grooming matrix may groom the electrical-layer signal converted from the optical signal according to the requirement for transferring service in the optical network, i.e., which wavelength of the optical signal should be transmitted to which output port. Therefore, no conflicts among electrical-layer signals will occur and the issue of optical wavelength conflicts can be addressed. The electrical-layer signal may be a single-wavelength electrical signal and/or a unified mapped container signal. Further, due to the characteristics of the electrical-layer grooming matrix, the electrical-layer signal from one input port can be directed to a plurality of output ports, i.e., multicast and/or broadcast service is realized. The electrical-layer matrix may be a cross connect chip for electrical layer. 
     The electrical-layer multiplexing unit  204  may multiplex the unified mapped container signal from the electrical-layer grooming unit  203  into high rate single-wavelength electrical signals in a direct interpolating manner or a bit interpolating manner. The electric-photo conversion unit  2052  performs an electric-photo conversion on the single-wavelength electrical signals and generates single-wavelength optical signals and outputs to the wavelength division multiplexing unit  2051 . The wavelength division multiplexing unit  2051  multiplexes the single-wavelength optical signals and outputs the single-wavelength optical signals. 
     In particular, the electrical-layer demultiplexing unit  202  and/or electrical-layer multiplexing unit  204  may employ a Mapping Processor (MAP processor). 
     In addition, the goal of the embodiments can be achieved without the electrical-layer demultiplexing unit  202  and the electrical-layer multiplexing unit  204 . The single-wavelength electrical signals converted by the photo-electric conversion unit  2012  may be input directly to the electrical-layer grooming unit  203  which grooms the single-wavelength electrical signals and outputs these signals to the electric-photo conversion unit  2052  directly. 
     Referring to  FIG. 3 , a grooming apparatus in an optical communication network is provided according to a second embodiment of the present invention. The apparatus is used to groom multi-dimensional multi-wavelengths loop service. The difference between the first embodiment and the second embodiment is that signals processed by the photoelectric integration unit  301  may be bidirectional. The photoelectric integration unit  301  includes a wavelength division multiplexing/demultiplexing unit  3011 , an electric-photo/photo-electric conversion unit  3012 . A MAP processor  302  provides demultiplexing and/or multiplexing functions. The data processed by the electrical-layer grooming unit  303  may be bidirectional. Bold solid lines with bidirectional arrows refer to inner-loop grooming. Dotted lines with bidirectional arrows refer to inter-loop grooming. 
     Referring to  FIG. 4 , a grooming apparatus in an optical communication network is provided according to a third embodiment of the present invention. The apparatus is used to groom the drop-loop in the local service. The apparatus includes a first photoelectric integration unit  401 , an electrical-layer demultiplexing unit  402 , an electrical-layer grooming unit  403 , and a demapping unit  404 . The first photoelectric integration unit  401  includes a wavelength division demultiplexing unit  4011  and a photo-electric conversion unit  4012 . The demapping unit  404  may include a unified container signal demapping unit  4042  and a service demapping unit  4041 . 
     A multi-wavelength optical signal is decomposed by the wavelength division demultiplexing unit  4011  into a plurality of single-wavelength optical signals. The single-wavelength optical signals undergo a photo-electric convention by a photo-electric conversion unit  4012  and become single-wavelength electrical signals which are subsequently output to the electrical-layer demultiplexing unit  402 . The first photoelectric integration unit  401  provides amplification, rectification, and re-timing functions. Moreover, it is capable of recovering the single-wavelength optical signal and compensating the dispersion occurred in the WDM system so as to compensate the light power loss. The electrical-layer demultiplexing unit  402  de-multiplexes the single-wavelength electrical signals and obtains a unified mapped container signal which is then output to the electrical-layer grooming unit  403 . 
     The electrical-layer grooming unit  403  grooms the unified mapped container signal and outputs the unified mapped container signal to the unified container signal demapping unit  4042 . 
     The unified container signal demapping unit  4042  demaps the unified mapping container signal and extracts the data frame. The unified mapped container signal may be a Virtual Container or Optical Channel Data Unit (ODU). The service demapping unit  4041  is used to demap the data frame, remove the data header, and extract service data. 
     The unified container signal demapping unit  4042  may utilize a MAP processor. 
     The goal of the present invention can be achieved without the electrical-layer demultiplexing unit  402 . That is, the single-wavelength electrical signals obtained from the photo-electric conversion unit  4012  are output directly to the electrical-layer grooming unit  403 . 
     Referring to  FIG. 5 , a grooming apparatus for an optical communication network is provided according to a fourth embodiment of the present invention. The apparatus is used to groom the add-loop of the local service. The apparatus includes a mapping unit  501 , an electrical-layer grooming unit  502 , an electrical-layer multiplexing unit  503 , and a second photoelectric integration unit  504 . The mapping unit  501  includes a service mapping unit  5011  and a unified container signal mapping unit  5012 . The second photoelectric integration unit  504  includes an electric-photo conversion unit  5042  and a wavelength division multiplexing unit  5041 . 
     The service mapping unit  5011  is configured to add data header to the service data to obtain a data frame. The unified container signal mapping unit  5012  is used to map the data frame into a unified mapped container signal based on the data header in a byte cross connect manner. The unified mapped container signal is then output to the electrical-layer grooming unit  502 . 
     The electrical-layer grooming unit  502  is configured to output the unified mapped signal to the electrical-layer multiplexing unit  503 . 
     The electrical-layer multiplexing unit  503  is configured to multiplex the unified mapped container signal from the electrical-layer grooming unit  502  into single-wavelength electrical signals and output these signals to the electric-photo conversion unit  5042 . 
     The electric-photo conversion unit  5042  is configured to perform an electric-photo conversion on the single-wavelength electrical signals generated from the electrical-layer multiplexing unit  503  to generate single-wavelength optical signals and output the optical signals to the wavelength division multiplexing unit  5041 . 
     The wavelength division multiplexing unit  5041  is configured to multiplex a plurality of single-wavelength optical signals into a multi-wavelength optical signal and output the multi-wavelength optical signal. 
     The unified container signal mapping unit  5012  may utilize a MAP processor. 
     Referring to  FIG. 6 , a grooming apparatus for an optical communication network is provided according to a fifth embodiment of the present invention. The apparatus is used to groom add/drop-loop of the local service. The difference between the fifth embodiment and the fourth/third embodiment is that signals processed by the photoelectric integration unit  601  may be bidirectional. The photoelectric integration unit  601  includes a wavelength division multiplexing/demultiplexing unit  6011 , and an electric-photo/photo-electric conversion unit  6012 . A MAP processor  602  provides demultiplexing and/or multiplexing functions. The data processed by an electrical-layer grooming unit  603 , a MAP processor  6042  and a service mapping/demapping unit  6041  may be bidirectional. The MAP processor  6042  may map/demap the unified container signal. 
     Referring to  FIG. 7 , a grooming apparatus for an optical communication network is provided according to a sixth embodiment of the present invention. The apparatus is configured to flexibly groom the multi-dimensional electrical wavelengths. The apparatus is capable of grooming the add/drop-loop of the local service and/or grooming the wavelength. Signals processed by a photoelectric integration unit  701  may be bidirectional. The photoelectric integration unit  701  includes a wavelength division multiplexing/demultiplexing unit  7011  and an electric-photo/photo-electric conversion unit  7012 . A MAP processor  702  provides demultiplexing and/or multiplexing functions. The signal processed by the MAP processor can be bidirectional. The Data processed by an electrical-layer grooming unit  703 , a MAP processor  7042  and a service mapping/demapping unit  7041  may be bidirectional. The MAP processor  7042  may map/demap the unified container signal. 
     Referring to  FIG. 8 , a grooming method for grooming wavelength in an optical communication network is provided according to a seventh embodiment of the present invention. The method includes the following steps. 
     Step  801 : A wavelength division demultiplexer de-multiplexes a multi-wavelength optical signal into a plurality of single-wavelength optical signals. 
     Step  802 : A photo-electric converter performs a photo-electric conversion on the single-wavelength optical signals and generates single-wavelength electrical signals. 
     Step  803 : The single-wavelength electrical signals is de-multiplexed to obtain a unified mapped container signal. 
     Step  804 : The unified mapped container signal is groomed. 
     Step  805 : The groomed unified mapped container signal is multiplexed into high-rate single-wavelength electrical signals in a direct interpolating manner or in a bit interpolating manner. 
     Step  806 : An electric-photo converter performs an electric-photo conversion on the single-wavelength electrical signals and generates single-wavelength optical signals. 
     Step  807 : A wavelength division multiplexer outputs a plurality of single-wavelength optical signals. 
     The goal of the present invention can also be achieved without step  803  and step  805 . At Step  804 , single-wavelength electrical signals may be groomed directly. 
     The high-rate single-wavelength electrical signals obtained at step  805  and the single-wavelength electrical signals generated at step  802  may or may not be the same signals. 
     The single-wavelength optical signals obtained at step  806  and the single-wavelength optical signals de-multiplexed at step  801  may or may not be the same signals. 
     The multi-wavelength optical signal multiplexed, at step  807 , from a plurality of single-wavelength optical signals and the multi-wavelength optical signal at step  801  may or may not be the same signal. 
     Referring to  FIG. 9 , a grooming method for grooming drop-loop of the local service in an optical communication network is provided according to an eighth embodiment of the present invention. The method includes the following steps. 
     Steps  901 ˜ 904  are similar to steps  801 ˜ 804 . 
     Step  905 : The unified mapped container signal is demapped to extract a data frame. 
     Step  906 : The data frame is demapped so as to obtain the service data. 
     Referring to  FIG. 10 , a grooming method for grooming add-loop of the local service in an optical communication network is provided according to a ninth embodiment of the present invention. The method includes the following steps. 
     Step  1001 : A data header is inserted into the service data to obtain a data frame. 
     Step  1002 : The data frame is mapped into a unified mapped container signal based on the data header in a byte cross connect manner. 
     Step  1003 : The unified mapped container signal is groomed. 
     Step  1004 : The groomed unified mapped container signal is multiplexed to obtain single-wavelength electrical signals. 
     Step  1005 : An electric-photo converter performs an electric-photo conversion on the single-wavelength electrical signals and generates single-wavelength optical signals. 
     Step  1006 : A wavelength division multiplexer multiplexes a plurality of single-wavelength optical signals into a multi-wavelength optical signal and outputs the multi-wavelength optical signal. 
     From the above analysis, technical effects as a result of the above proposed solutions according to the present invention are described below. 
     1. In an embodiment of the present invention, a photoelectric integration unit is provided to perform photo-electric conversion or electric-photo conversion. The photoelectric integration unit provides amplifications, rectification, and re-timing functions. Moreover, the photoelectric integration unit is able to recover the single-wavelength optical signal and is also able to compensate light dispersion so as to compensate the light power loss. 
     2. In an embodiment of the present invention, a photoelectric integration unit is employed to perform an optical-electric-photo conversion. Light noise accumulation issue may be eliminated in the optical network so that the problem of restricted management on light signal-to-noise ratio can be solved. 
     3. In an embodiment of the present invention, an MAP processor is provided to process the unified mapped container signal. An overhead byte defined by the mapped container may be employed to track the wavelength and/or service data in the network in real time so that the problem of restricted grooming on wavelength is addressed. 
     4. In an embodiment of the present invention, an electrical-layer grooming unit is provided to groom the single-wavelength electrical signals. Due to the characteristics of the electrical-layer grooming method employed by the electrical-layer grooming unit, wavelength conflict is eliminated, and broadcast and/or multicast service can be realized. 
     5. In an embodiment of the present invention, the photoelectric integration unit, the electrical-layer grooming unit, and the MAP processor, etc., are utilized to constitute a low cost system for flexibly grooming the multi-dimensional optical wavelength based on electricity. 
     Grooming methods and systems in an optical communication network according to embodiments of the present invention are presented above in details. Several specific examples are given to the present invention to illustrate the principle and implementation of the present invention. The description of the embodiments is intended merely to facilitate the understanding of the method and key ideas of the present invention. Further, it is readily appreciated by those skilled in the art that any modification can be made to the specific implementation and application field without departing from the spirit and scope of the present invention. Accordingly, the content of the specification shall not be construed as a limitation to the present invention.