Abstract:
An optical transceiver includes a transmitter that transmits an optical signal, and a receiver that receives a reference signal. The receiver receives the optical signal transmitted by its own transmitter. A controller performs an adjustment of the optical signal, transmitted by the transmitter, based on the reference signal.

Description:
BACKGROUND 
       [0001]    This document relates to an optical transceiver, and more particularly, to the adjustment of transmitter signals. 
       RELATED ART 
       [0002]    Patent Literature 1 discloses an optical communication method and an optical transceiver. In the optical communication method according to Patent Literature 1, the optical transceiver acquires information about the transmission rate and data format of a baseband signal from an external interface. The optical transceiver also transmits to and receives from another optical transceiver a test signal at a transmission rate and in a transmission format that is set based on the information from the external interface. In addition, the optical transceiver sets a transmission rate and transmission format by comparing the transmission rate, set to transmit the test signal, with the transmission rate of the received test signal, and then transmits and receives information about data formats so as to select a data format. According to Patent Literature 1, this approach is said to allow the optical transceiver to be compatible with signals at various transmission rates, in various data formats and transmission formats, with a simple assembly including a single physical interface. 
         [0003]    Patent Literature 1, in particular, is Japanese Unexamined Patent Application Publication No. 2005-229298. Optical transceivers, such as an SFP (small form-factor pluggable) and an XFP (10 gigabit small form-factor pluggable), have a region for storing values, adjusted to impart desired characteristics to the optical transceivers, in a storage area in addition to a memory map, in conformity with a MSA (multi source agreement). 
         [0004]    The firmware of such optical transceivers has not only a normal mode of regulating the operation in normal usage, but also an adjustment mode of regulating the operation so as to adjust the optical transceivers. In general, access from external components to the region storing the adjusted value for the optical transceiver is disabled in the normal mode, but is enabled in the adjustment mode. 
         [0005]      FIG. 10  illustrates a general configuration when adjustment processing is performed. The characteristics, including the waveform, of a transmitter signal from an optical transceiver  101 , are measured by an external measurement apparatus  102  including a power meter  111 , optical waveform measuring device  112 , and so on. An adjustment program  121  in a personal computer  103  determines an adjusted value of the transmitter signal based on the characteristic information of the transmitter signal obtained from the external measurement apparatus  102 , and makes access to firmware  131  of the optical transceiver  101  via an I2C communication to store the adjusted value into an adjustment memory map  132 . The firmware  131  of the optical transceiver  101  adjusts the waveform of the transmitter signal based on the adjusted value stored in the adjustment memory map  132 . This series of actions is repeatedly performed until a transmitter signal, with a desired waveform, is obtained. 
         [0006]    In factories that manufacture the optical transceivers, adjustment, test and other processes are performed to impart the desired characteristics to the optical transceivers. The adjustment, test, and the other processes are generally performed automatically by a program through communication between the optical transceiver and the measurement apparatuses. 
         [0007]    Such factories can prepare the aforementioned testing program suitable for the factory-owned measurement apparatuses because the test is conducted in conformity with the MSA (multi source agreement). Even if the factories are EMS (Electronics Manufacturing Service) providers, a common testing program can be shared in many cases irrespective of the design of transceivers of the commissioning parties. 
         [0008]    However, in the case of the adjustment program in which the address of an adjusted-value storing region, the range of adjusted values, and other factors vary by the design of the transceiver of the commissioning party, a new adjustment program often has to be prepared for each design. In addition, if the commissioned party of the EMS is changed to another, the program needs to be modified in accordance with the measurement apparatus owned by the new commissioned party. 
       SUMMARY 
       [0009]    To solve the problems, the exemplary embodiments provide a widely usable adjustment program under varying measurement environments. However, the exemplary embodiments may achieve objectives other than those described above. Further, exemplary embodiments are not required to achieve the objectives described above, and an exemplary embodiment may not achieve any of the objectives described above. 
         [0010]    A first aspect of the exemplary embodiment is directed to an optical transceiver including a transmission unit, a reception unit, and a control unit. The control unit, operated by firmware provided in the optical transceiver, performs adjustment processing of adjusting a transmitter signal, transmitted by the transmission unit, based on a reference signal. In the adjustment processing, the control unit acquires the reference signal via reference-signal output unit and the reception unit, and acquires the transmitter signal by a connection of the transmission unit to the reception unit. 
         [0011]    A second aspect of the exemplary embodiment is directed to a method for adjusting a transmitter signal of an optical transceiver. The method includes a step of performing adjustment processing, of adjusting a transmitter signal based on a reference signal, by firmware provided in the optical transceiver, a step of acquiring the reference signal from a source that outputs the reference signal and a receiver that receives it, in the adjustment processing, and a step of acquiring the transmitter signal by connecting the output of the transmitter signal and the input to the receiver, in the adjustment processing. 
         [0012]    A third aspect of the exemplary embodiment is directed to an adjustment program for adjusting a transmitter signal of an optical transceiver. The adjustment program requests a computer that controls the optical transceiver to perform adjustment processing of adjusting the transmitter signal based on a reference signal, processing of acquiring the reference signal by operationally connecting a source that outputs the reference signal and a receiver in the adjustment processing, and processing of acquiring the transmitter signal by connecting the output of the transmitter signal to the receiver in the adjustment process. 
         [0013]    Thus, the adjustment of transmitter signals can be carried out without resort to an external system, such as an external measurement apparatus, and without depending on a personal computer for adjustment. This makes it possible to use an adjustment program without substantial change even when the measurement environment is changed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  illustrates a functional configuration of an optical transceiver according to the first exemplary embodiment. 
           [0015]      FIG. 2  illustrates by an example a configuration of hardware of the optical transceiver according to the first exemplary embodiment. 
           [0016]      FIG. 3  is a flow chart showing processing steps for adjusting the transmitter signal by the firmware according to the first exemplary embodiment. 
           [0017]      FIG. 4  illustrates connection between the optical transceiver and an external system in a state of waiting for a reference signal. 
           [0018]      FIG. 5  illustrates connection between the optical transceiver and the external system in a state of waiting for a transmitter signal. 
           [0019]      FIG. 6  illustrates by an example a configuration of hardware of an optical transceiver according to the second embodiment. 
           [0020]      FIG. 7  illustrates by an example a configuration of hardware of an optical transceiver according to the third embodiment. 
           [0021]      FIG. 8  illustrates by an example a configuration of hardware of an optical transceiver according to the fourth embodiment. 
           [0022]      FIG. 9  illustrates connection between the optical transceiver and an external system in a state of waiting for a reference signal according to the fifth embodiment. 
           [0023]      FIG. 10  illustrates by an example a general configuration of an optical transceiver that adjusts transmitter signals. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    With reference to the drawings, exemplary embodiments will be described.  FIG. 1  illustrates a functional configuration of an optical transceiver  1  according to the first exemplary embodiment. The optical transceiver  1  includes a transmission unit  2 , a reception unit  3 , and a control unit  4 . The word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. 
         [0025]    The transmission unit  2  outputs transmitter signals used, normally, for communication to other optical transceivers or other components ( FIG. 1  does not illustrate such a mode). The reception unit  3  inputs receiver signals from the other optical transceivers or the other components. 
         [0026]    The control unit  4  is controlled by firmware  5  to control not only the transmission unit  2 , reception unit  3 , and regular communication processing, but also adjustment processing to adjust the transmitter signals based on a reference signal. That is to say, the control unit  4  controls whether the optical transceiver  1  is operated in a normal mode for communication with other optical transceivers, or whether it is operated in an adjustment processing mode in, e.g., a factory in which an adjustment processing is carried out prior to shipping. 
         [0027]    To execute the adjustment processing, the control unit  4  connects a reference-signal output unit  6 , which supplies reference signals, and the reception unit  3  to obtain the characteristics of a reference signal, and connects the transmission unit  2  and reception unit  3  to obtain the characteristics of a transmitter signal. In addition, the control unit  4  performs the adjustment processing, under control of the firmware  5 , based on the characteristics of the reference signal and the transmitter signal obtained via the reception unit  3 . 
         [0028]    The above-described configuration can make the program for adjustment processing widely usable even if the measurement environment changed. 
         [0029]      FIG. 2  illustrates the hardware configuration of the optical transceiver  1  according to the present embodiment. The optical transceiver  1  includes a microcontroller  11 , D/A converters  12 A,  12 B, a transmitter circuit  13 , a transmitter module  14 , A/D converters  15 A,  15 B, a receiver circuit  16 , and a receiver module  17 . The microcontroller is an information processing unit composed of a CPU controlling the whole optical transceiver  1 , memory and other components. The memory stores firmware  5 , an MSA memory map  21 , an adjustment memory map  22 , and so on. The transmitter circuit  13  includes a bias drive circuit  25  and a variable drive circuit  26 , while the receiver circuit  16  includes an amplitude detection circuit  27  and an average-value detection circuit  28 . 
         [0030]    An optical signal received by the optical receiver module  17  is converted into an electrical signal and input to the receiver circuit  16 . The electrical signal having entered the receiver circuit  16  is analyzed by the amplitude detection circuit  27  and average-value detection circuit  28  that detect the characteristics, such as an output amplitude and optical output power, of the signal. These characteristics are represented by analog signals that are in turn converted by the A/D converters  15 A,  15 B, respectively, into digital signals and input to the microcontroller  11 . Thus, the firmware  5  mounted in the microcontroller  11  acquires the characteristics, such as waveforms, of the optical signal, which is input to the receiver module  17 , in the form of a digital signal. 
         [0031]    The firmware  5  outputs digital control signals for driving the transmitter module  14  to the D/A converters  12 A,  12 B. The bias drive circuit  25  and variable drive circuit  26  of the transmitter circuit  13  drives the transmitter module  14  in response to the analogue control signals input from the D/A converters  12 A,  12 B, respectively. The transmitter module  14  outputs a transmitter signal having a waveform adjusted by the microcontroller  11 . 
         [0032]      FIG. 3  shows processing steps to adjust transmitter signals by the firmware  5 . When power is turned on to activate the optical transceiver  1 , the firmware  5  starts operation mode determination to determine whether the optical transceiver  1  is in an adjustment mode (S 101 ). One method to determine the mode, for example, includes setting a flag bit for determination on the adjustment map  22 . Setting the initial value of the flag bit so as to move to the adjustment mode when the FW program is running allows the flag bit to move to the adjustment mode on startup for the first time. If it is determined that the optical transceiver is not in the adjustment mode (or adjustment has been completed) (NO) in step S 101 , the optical transceiver goes to a normal mode (S 108 ). 
         [0033]    In step S 101 , if it is determined that the optical transceiver is in the adjustment mode (YES), the optical transceiver  1  enters a state of waiting for input of a reference signal (S 102 ).  FIG. 4  illustrates connection between the optical transceiver  1  and an external system in a state of waiting for the reference signal. At this moment, the optical transceiver  1  is connected, with a reference transceiver  31  and the personal computer  35 . The reference transceiver  31  is connected with the receiver module  17  of the optical transceiver  1  to transmit a reference signal. The personal computer  35  includes an adjustment program  36  that is operatively associated with the firmware  5  of the optical transceiver  1  to contribute to execution of the adjustment processing. 
         [0034]    When the reference signal is received via the receiver module  17  (YES) in step S 102 , information representing the characteristics, such as waveforms, of the reference signal is stored (S 103 ). The processes of acquiring and storing the characteristics of the reference signal are performed by the firmware  5  of the optical transceiver  1 . With these processes, the output power (REF_POW) and output amplitude (REF_AMP) of the reference signal are acquired in the form of a digital signal. The acquired characteristic information of the reference signal is stored in the adjustment memory map  22  as a target value of a transmitter signal. 
         [0035]    Then, the optical transceiver  1  enters a state of waiting for a transmitter signal (S 104 ).  FIG. 5  illustrates connection between the optical transceiver  1  and the external system in a state of waiting for the transmitter signal. At this moment, the reference transceiver  31  is disconnected from the receiver module  17  of the optical module  1  and the transmitter module  14  is connected to the receiver module  17 . 
         [0036]    In step S 104 , if the transmitter signal is received via the receiver module  17  (YES), information representing the characteristics, such as waveforms, of the transmitter signal is stored. The processes of acquiring and storing the characteristics of the transmitter signal are performed by the firmware  5  of the optical transceiver  1 . With these processes, the output power (OUT_POW) and output amplitude (OUT_AMP) of the transmitter signal are acquired in the form of a digital signal. 
         [0037]    Then, the characteristic information of the transmitter signal is adjusted to be close to the REF_POW and REF_AMP stored in the adjustment memory map  22  as targets (S 105 ). This adjustment can be made by the firmware  5  in the same procedures that are conventionally performed by an adjustment program. 
         [0038]    The adjusted characteristic information of the transmitter signal is stored in the adjustment memory map  22  by the firmware  5 , and the adjustment mode is terminated (S 107 ). If a flag bit is used to determine the operation mode (S 101 ) as described above, the termination processing of the adjustment mode is performed by setting the flag to a value that sends the optical transceiver into the normal mode. Upon startup of the optical transceiver  1  after termination of the adjustment processing, the optical transceiver is determined to be in the operation mode in the determination step (S 101 ) and then performs normal operation. 
         [0039]    According to the optical transceiver  1 , adjustment of the transmitter signal can be made without external measurement apparatuses, such as a power meter and an optical waveform measuring device. In addition, adjustment of the transmitter signal can be made without making access from the external system, such as the personal computer  35 , to the adjustment memory map  22 . Accordingly, it is possible to widely use the adjustment program under varying measurement environments. 
       Second Embodiment 
       [0040]      FIG. 6  illustrates the hardware configuration of an optical transceiver  41  according to the second exemplary embodiment. In the optical transceiver  41 , the A/D converters  15 A,  15 B and D/A converters  12 A,  12 B are implemented as functions in the microcontroller  11 . 
       Third Embodiment 
       [0041]      FIG. 7  illustrates the hardware configuration of an optical transceiver  51  according to the third exemplary embodiment. In the optical transceiver  51 , functions  25 ,  26  on the transmitter side and functions  27 ,  28  on the receiver side are implemented as functions of a single transmitter-receiver circuit  52 . 
       Fourth Embodiment 
       [0042]      FIG. 8  illustrates the hardware configuration of an optical transceiver  61  according to the fourth exemplary embodiment. In the optical transceiver  61 , the A/D converters  15 A,  15 B, the D/A converters  12 A,  12 B, and transmitter and receiver functions  25 ,  26 ,  27 ,  28  are implemented by a single transmitter-receiver circuit  62 . 
       Fifth Embodiment 
       [0043]      FIG. 9  illustrates connection between an optical transceiver  71  and an external system in a state of waiting for a reference signal according to the fifth exemplary embodiment. In the embodiment, an optical switch  72  is interposed between the optical transceiver  71  and a reference transceiver  31 . 
         [0044]    The optical switch  72  can switch between a reference signal from the reference transceiver  31  and a transmitter signal from the transmitter module  14  to send one of these to the receiver module  17 . The switching is controlled by the adjustment program  36  on the personal computer  35 . Specifically, the optical switch  72  is controlled to connect the reference transceiver  31  with the receiver module  17  in step S 102  of the adjustment processing shown in  FIG. 3  and to connect the transmitter module  14  with the receiver module  17  in step S 104 . 
         [0045]    The configuration according to the second to fifth exemplary embodiments can also provide the same effects as the first exemplary embodiment. 
         [0046]    It should be noted that the present invention is not limited to the above exemplary embodiments but modification can be made as needed without deviating from the spirit and scope the invention as defined by the claims. 
       EXPLANATION OF REFERENCE NUMERALS 
       [0000]    
       
           1 ,  41 ,  51 ,  61 ,  71  optical transceiver 
           2  transmission unit 
           3  reception unit 
           4  control unit 
           5  firmware 
           11  microcontroller 
           12 A,  12 B D/A converter 
           13  transmitter circuit 
           14  transmitter module 
           15 A,  15 B A/D converter 
           16  receiver circuit 
           17  receiver module 
           21  MSA memory map 
           22  adjustment memory map 
           25  bias drive circuit 
           26  variable drive circuit 
           27  amplitude detection circuit 
           28  average-value detection circuit 
           31  reference transceiver 
           35  personal computer 
           36  adjustment program 
           52 ,  62  transmitter-receiver circuit 
           72  optical switch