JP2009005308A - Optical signal transmitter and optical signal transmission apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical signal transmitter capable of generating alarm when a bit rate is varied on a transmission line, and to provide an optical signal transmission apparatus using the optical signal transmitter. <P>SOLUTION: The optical signal transmitter 30, which sends an optical signal to an optical transmission line, comprises: a modulation driving circuit 1 which generates a driving data signal for driving an optical modulator 2 based on an inputted data code signal; a sine wave superimposing circuit 3 for superimposing a low-frequency sine wave on the driving data signal; the optical modulator 2 which performs optic/electric conversion on the driving data signal on which the low-frequency sine wave has been superimposed to produce an optical output signal; and a sine wave extracting circuit 5 which extracts a sine wave component contained in the optical output signal, monitors the bit rate of the optical output signal based on the extracted sine wave component, and issues a warning signal in a case where it is judged that the bit rate is varied. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical signal transmitter that converts an electrical signal into an optical signal and transmits the optical signal, and an optical signal transmission device using the optical signal transmitter.

  FIG. 6 shows a configuration of an optical signal transmission apparatus related to the present invention. The optical signal transmission apparatus includes an optical signal receiver 10 and an optical signal transmitter 20. The optical signal transmitter 20 receives a data code signal and a clock signal obtained by photoelectric conversion, clock extraction, and signal identification reproduction of the optical signal received by the optical signal receiver 10. The optical signal transmitter 20 operates depending on the data code signal and the clock signal input from the optical signal transmitter 10.

FIG. 7 shows the configuration of the optical signal transmitter 20. The optical signal transmitter 20 includes a modulator driving circuit 21 and an optical modulator 22.
A data code signal and a clock signal are input to the modulator drive circuit 21. The modulator drive circuit 21 generates drive data for driving the optical modulator 22 synchronized with the data code signal and the clock signal. The optical modulator 22 receives the drive data from the modulator drive circuit 21, converts the electrical signal into an optical signal, and sends it to the transmission line.

  Transmission devices have standards such as SONET and SDH, Ethernet (registered trademark) standards, fiber channel standards, and the like, and have different bit rates as shown in FIG.

  When an optical receiver that does not depend on the bit rate is used in a transmission apparatus on a network in which signals of these different bit rates are mixed, the bit rate that is actually transmitted with respect to the bit rate of the signal set by the transmission apparatus Even if a signal with a bit rate different from the setting is input, photoelectric conversion, clock extraction, and signal identification / reproduction are possible, so that a data code signal and a clock signal with a bit rate different from the setting are generated. The

  However, since the optical signal transmitter 20 cannot recognize the bit rate, it cannot issue a warning even if the bit rate fluctuates.

  In this case, since the optical signal transmitter 20 operates without a warning with an unset bit rate signal, a failure occurs in the transmission apparatus.

As a technique related to transmission / reception of an optical signal, there is an “optical cross-connect device having transparency” disclosed in Patent Document 1 and an “optical transmitter” disclosed in Patent Document 2.
The invention disclosed in Patent Document 1 detects a bit rate based on data / CLK received by an optical receiver. The invention disclosed in Patent Document 2 superimposes a low frequency clock on a data waveform to shape an optical transmission waveform.
JP 2001-244906 A JP 2004-247968 A

However, since the invention disclosed in Patent Document 1 is configured to detect the bit rate based on the data / CLK received by the optical receiver, the bit rate cannot be detected correctly when a failure occurs in the transmission path. There is sex.
The invention disclosed in Patent Document 2 relates to a modulation scheme of an optical transmitter, and is not intended to detect a bit rate.
In addition, since the invention disclosed in Patent Document 1 relates to an optical receiver and the invention disclosed in Patent Document 2 relates to an optical transmitter, it is difficult to combine them and low frequency It is impossible to detect the bit rate using a clock with an optical receiver.

  That is, the invention disclosed in the above-mentioned patent document cannot detect the bit rate by the optical receiver. Thus, conventionally, an optical signal transmitter capable of issuing a warning when a change in bit rate occurs in a transmission line has not been realized.

  The present invention has been made in view of such problems, and provides an optical signal transmitter capable of issuing a warning when a bit rate fluctuation occurs in a transmission line and an optical signal transmission device using the same. Objective.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided an optical signal transmitter for transmitting an optical signal to an optical transmission line, wherein the optical modulation means is driven based on an input data code signal. Drive data generating means for generating a drive data signal, a sine wave superimposing means for superimposing a low-frequency sine wave on the drive data signal, and a drive data signal on which the low-frequency sine wave is superimposed is photoelectrically converted to light When the optical modulation means that generates the output signal and the sine wave component included in the optical output signal are extracted, the bit rate of the optical output signal is monitored based on the extracted sine wave component, and it is determined that the bit rate has changed An optical signal transmitter having warning means for issuing a warning signal is provided.

  In the first aspect of the present invention, the warning means monitors the bit rate of the optical output signal based on the sine wave extraction means for extracting the sine wave component included in the optical output signal and the extracted sine wave component, It is preferable to have a monitoring unit that issues a warning signal when it is determined that the bit rate has changed. In addition, the sine wave extracting unit includes a photoelectric conversion unit that photoelectrically converts an optical output signal, and the photoelectric conversion unit. It is preferable to have band-passing means for passing the frequency band of the low-frequency sine wave among the electrical signals output from the.

  In the configuration including the monitoring unit according to the first aspect of the present invention, the monitoring unit determines that the bit rate of the optical output signal fluctuates when the fluctuation of the peak value of the sine wave component exceeds a predetermined fluctuation range. It is preferable to judge. The monitoring means preferably compares the peak value of the sine wave component with the peak value information for each bit rate recorded in advance to identify the bit rate of the optical output signal and outputs it as bit rate information.

  In any of the above configurations of the first aspect of the present invention, it is preferable that the drive data generation means generates a drive data signal synchronized with a clock signal supplied together with the data code signal. The sine wave superimposing means preferably superimposes the low frequency sine wave on the drive data signal via a coil having a high impedance with respect to the drive data signal and a low impedance with respect to the low frequency sine wave. The light modulation means preferably comprises a Mach-Zehnder type external modulator and a laser light source.

  In order to achieve the above object, the present invention provides, as a second aspect, an optical signal transmitter according to any one of the above configurations of the first aspect of the present invention, and data obtained by photoelectrically converting an optical input signal. An optical signal transmission apparatus including an optical signal receiver that generates a code signal and outputs the code signal to an optical signal transmitter is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the optical signal transmitter which can issue a warning when the fluctuation | variation of a bit rate arises in a transmission line, and an optical signal transmission apparatus using the same can be provided.

[Example 1]
FIG. 1 shows the configuration of an optical signal transmitter of an optical signal transmission apparatus according to a first embodiment in which the present invention is suitably implemented. This optical signal transmitter is arranged at the subsequent stage of the optical signal receiver, as in the example shown in FIG.
The optical signal transmitter 30 includes a modulator driving circuit 1, an optical modulator 2, a sine wave superimposing circuit 3, an optical branch 4, and a sine wave extracting circuit 5.

  A data code signal and a clock signal are input to the modulator drive circuit 1. The modulator drive circuit 1 generates a drive data signal synchronized with the data code signal and the clock signal. The optical modulator 2 includes a Mach-Zehnder external modulator and a laser light source. The optical modulator 2 converts an electrical signal into an optical signal. The sine wave superimposing circuit 3 superimposes a sine wave having a frequency f on the drive data signal. The optical branch 4 branches the transmitted optical output signal into two, one is sent to the transmission line, and the other is input to the sine wave extraction circuit 5. The sine wave extraction circuit 5 extracts a sine wave from the drive data signal on which the sine wave is superimposed. The sine wave extraction circuit 5 monitors the fluctuation of the bit rate based on the extracted sine wave component amount, and sends alarm information when the fluctuation is detected.

FIG. 2 shows the configuration of the sine wave extraction circuit 5. The sine wave extraction circuit 5 includes an optical / electrical conversion circuit 51, a band pass filter 52, and an amplitude monitoring circuit 53.
The optical signal input from the optical branch 4 is converted into an electrical signal by the optical / electrical conversion circuit 51. The converted electrical signal is input to a bandpass filter 52 that transmits the frequency band of the superimposed sine wave, and the sine wave is reproduced. The reproduced sine wave is input to the amplitude monitoring circuit 53. The amplitude monitoring circuit 53 monitors the peak value of the amplitude of the sine wave. When the bit rate fluctuates, the frequency component of the sine wave fluctuates, and the peak value fluctuates accordingly. The amplitude monitoring circuit 53 monitors the fluctuation of the peak value, and when it exceeds a predetermined fluctuation range, determines that the bit rate has fluctuated, and transmits alarm information.

  FIG. 3 shows a connection state between the modulator driving circuit 1 and the sine wave superimposing circuit 3. The modulator driving circuit 1 and the sine wave superimposing circuit 3 are connected via a coil 100. The drive data signal output from the modulator drive circuit 1 is superimposed on the sine wave output from the sine wave superimposing circuit 3 and passing through the coil 100. The coil 100 exhibits a high impedance for the bit rate frequency to be used, and a low impedance in the frequency band of the superimposed sine wave.

The frequency component detection principle will be described with reference to FIG.
(A) shows the modulation characteristic of the Mach-Zehnder type external modulator. (B) shows the waveform of the drive data signal and the superimposed sine wave. (C) shows an optical output signal on which a sine wave is superimposed.
Here, it is assumed that the left side of (b) and the upper side of (c) correspond to the mark side, and the right side of (b) and the lower side of (c) correspond to the space side. It is the same.

  As shown in FIG. 4B, the drive data signal has a changing point that changes from the mark side to the space side or from the space side to the mark side (upper and lower diagonal lines in FIG. 4B). . The same sine wave is superimposed on the drive data signal regardless of whether it is the mark side, the space side, or the change point. As shown in FIG. 4A, the Mach-Zehnder type external modulator has a characteristic in which the light modulation characteristic corresponds to cosine square. Therefore, as shown in FIG. The sine wave component decreases at the space side and the sine wave component increases at the change point of the data code signal. As shown in FIG. 4C, the optical output signal on which the sine wave is superimposed has a superimposed waveform in the same phase on the mark side and the space side of the optical output signal.

Therefore, when looking at the waveform of the optical output signal on which the sine wave is superimposed, the more the number of changes from the mark side to the space side or vice versa within the unit time, the more frequency components are included. That is, since the higher bit rate has more changing points (left and right diagonal lines in FIG. 4C), the changing point is obtained when the superimposed sine wave has the same phase on the mark side and the space side. The frequency component increases when there is more. For this reason, when the bit rate fluctuates, the frequency component decreases, and the peak value of the extracted sine wave decreases. Conversely, when the bit rate fluctuates higher, the frequency component increases and the peak value of the extracted sine wave increases.
When the fluctuation of the peak value exceeds the predetermined fluctuation range, the amplitude monitoring circuit 53 recognizes that the bit rate has fluctuated and transmits an alarm signal.

When a data waveform with low frequency superimposed is modulated to optical output using a Mach-Zehnder type optical modulator, the modulation characteristic is the square of the sine wave, so on the space side / mark side (maximum point and minimum point in the modulation characteristic) Since the optical output characteristics are flat (slope 0), the superimposed waveform is compressed and the frequency component is reduced. However, since the frequency component is modulated as it is on the change side of the optical output characteristic, it is modulated while the frequency component remains large.
Considering the number of changing sides in a unit time (for example, 1 second), since a normal signal is transmitted at a mark rate of 1/2, the number of changing sides increases in proportion to the bit rate. That is, OC12 (622 Mbps) has four times the change side compared to OC-3 (155 Mbps). OC48 (2488 Mbps) further has a fourfold change side. If a low-frequency component is extracted from the optical output waveform using this fact, the low-frequency component differs depending on the bit rate being used, so that the bit rate being used can be determined.

  Thus, since the transmission apparatus using the optical signal transmitter 30 according to the present embodiment monitors the bit rate variation, it can grasp that the bit rate variation has occurred in the transmission path. As a result, an alarm can be issued when the bit rate changes upstream in an optical transmission system using an optical signal receiver that can extract a clock signal without depending on the signal frequency.

  Even when the optical signal receiver does not perform clock extraction and operates only with the data code signal, since the clock signal is not used for bit rate monitoring, the optical signal transmitter 30 can monitor the bit rate, and the upstream An alarm can be issued when the bit rate fluctuates.

  As described above, in this embodiment, it is possible to monitor the transmission apparatus using the optical receiver that has not extracted the clock so that the operation at the wrong bit rate is not performed.

[Example 2]
A second embodiment in which the present invention is suitably implemented will be described.
FIG. 5 shows the configuration of the optical signal transmitter according to the present embodiment. The configuration is the same as that of the first embodiment except that the sine wave extraction circuit 5 sends not only alarm information but also bit rate information.
Since the peak value of the amplitude of the extracted sine wave corresponds to the bit rate, the sine wave extraction circuit 5 estimates the operating bit rate from the peak value of the amplitude of the extracted low-frequency sine wave to estimate the bit rate. Output information. The peak value detected by the sine wave extraction circuit 5 is compared with the peak value information for each bit rate recorded in the initial stage, and when it matches the information, the bit rate information is determined as the recorded bit rate. Is output.

  Thus, the optical signal transmitter according to the present embodiment can estimate the operating bit rate based on the detected peak value of the amplitude of the sine wave.

  In addition, each said Example is an example of the suitable implementation of this invention, and this invention can be variously deformed without being limited to this.

It is a figure which shows the structure of the optical signal transmitter which concerns on 1st Example of this invention. It is a figure which shows the structure of a sine wave extraction circuit. It is a figure which shows the connection normal state of a modulator drive circuit and a sine wave superposition circuit. It is a figure which shows the detection principle of a frequency component. It is a figure which shows the structure of the optical signal receiver which concerns on a 2nd Example. It is a figure which shows the structure of an optical repeater. It is a figure which shows the structure of an optical signal transmitter. It is a figure which shows the difference in the bit rate by a communication standard.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,21 Modulator drive circuit 2 Optical signal transmitter 3 Sine wave superposition circuit 4 Optical branching 5 Sine wave extraction circuit 10 Optical signal receiver 20, 30 Optical signal transmitter 22 Optical modulator 51 Optical / electrical conversion circuit 52 Band pass Filter 53 Amplitude monitoring circuit 100 Coil

Claims (9)

An optical signal transmitter for sending an optical signal to an optical transmission line,
Drive data generation means for generating a drive data signal for driving the light modulation means based on the input data code signal;
Sine wave superimposing means for superimposing a low-frequency sine wave on the drive data signal;
The light modulation means for photoelectrically converting the drive data signal on which the low-frequency sine wave is superimposed to generate an optical output signal;
Warning means for extracting a sine wave component contained in the optical output signal, monitoring the bit rate of the optical output signal based on the extracted sine wave component, and issuing a warning signal when it is determined that the bit rate has fluctuated; An optical signal transmitter.   The warning means is a sine wave extraction means for extracting a sine wave component included in the optical output signal, and monitors the bit rate of the optical output signal based on the extracted sine wave component, and determines that the bit rate has fluctuated. 2. An optical signal transmitter according to claim 1, further comprising monitoring means for issuing a warning signal in the event of failure.   The sine wave extracting means includes photoelectric conversion means for photoelectrically converting the optical output signal, and band passing means for passing the frequency band of the low-frequency sine wave among electric signals output from the photoelectric conversion means. The optical signal transmitter according to claim 2.   The said monitoring means judges that the bit rate of the said optical output signal was fluctuate | varied, when the fluctuation | variation of the peak value of the said sine wave component exceeded the predetermined fluctuation range. Optical signal transmitter.   The monitoring means compares the peak value of the sine wave component with peak value information for each bit rate recorded in advance, identifies the bit rate of the optical output signal, and outputs it as bit rate information. The optical signal transmitter according to any one of claims 2 to 4.   6. The optical signal transmitter according to claim 1, wherein the drive data generation unit generates the drive data signal synchronized with a clock signal supplied together with the data code signal.   The sine wave superimposing means superimposes the low frequency sine wave on the drive data signal through a coil having a high impedance with respect to the drive data signal and a low impedance with respect to the low frequency sine wave. The optical signal transmitter according to any one of claims 1 to 6.   8. The optical signal transmitter according to claim 1, wherein the optical modulation means includes a Mach-Zehnder type external modulator and a laser light source. An optical signal transmitter according to any one of claims 1 to 8,
An optical signal transmission apparatus comprising: an optical signal receiver that photoelectrically converts an optical input signal to generate the data code signal and outputs the data code signal to the optical signal transmitter.

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