JP2007201540A - Optical signal transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical signal transmitter for a burst signal capable of generating an optical signal including a non-signal state without causing waveform distortion. <P>SOLUTION: The optical signal transmitter includes: a light source (101) including therein an optical gate; and an external modulator (102) for modulating the light from the light source with an electric signal including a data signal to be transmitted. The light source includes therein the optical gate (108), which controls transmission/shut-off of the optical signal according to a control signal. The control signal applied to the optical gate is a signal whose timing is matched with the timing of the electric signal and equivalent to an envelope of the data to be transmitted. The electric signal is a signal resulting from inserting a signal whose transmission rate is nearly equal to that of the data signal between meaningful data lumps to eliminate a low frequency signal component. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical signal transmitter for generating an optical signal generated intermittently, and more particularly to an optical signal transmitter for burst communication.

  A wavelength division multiplexing (WDM) transmission system in which a plurality of optical signals are placed on light of different wavelengths and transmitted through a single optical fiber can greatly increase the capacity of the transmission path, Introduction is progressing mainly in mission-critical systems. Furthermore, in recent years, not only is the wavelength of an optical signal applied to an increase in transmission path capacity, but also development and introduction of wavelength routing that is used for setting a network path has been advanced.

  In such a photonic network system utilizing wavelength information, in order to efficiently use network resources without waste, application of a technique called burst communication is effective.

  In burst communication, data to be transmitted is collected for each destination, and transmitted and received as a series of data chunks. When this burst communication is applied to a photonic network that utilizes wavelength information, a transmitter that incorporates a wavelength tunable light source is used, and data collected for each destination is transmitted as a signal of an appropriate wavelength. . In a conventional photonic network system that does not support such burst communication and does not use a wavelength tunable light source, it is necessary to assign a unique light source even to a route with low traffic, and the use efficiency of network resources is reduced. It was. On the other hand, if burst communication is applied, it is possible to use a transmitter with a built-in wavelength tunable light source instead of multiple transmitters that were used on a route with relatively little traffic, improving network resource utilization efficiency. (Non-Patent Document 1).

  However, it is not easy to generate a signal used for burst communication. FIG. 4 shows a configuration of a conventional typical high bit rate optical signal transmission apparatus. In FIG. 4, 401 is a light source, 402 is an external modulator, 403 is a data signal input port for inputting an electrical data signal, 404 is a bias power supply, 405 is a driver circuit for an external modulator, and 406 is an optical signal output port. . A data signal, which is an electrical signal input from the data signal input port 403, is input to the external modulator driver circuit 405 and amplified to an appropriate desired amplitude. The amplified data signal is further supplied from the bias power supply 404 to the outside. In response to the DC voltage supplied to the modulator driver circuit 405, the signal is output from the external modulator driver circuit 405 as an appropriate average voltage signal. The electrical signal output from the external modulator driver circuit 405 is input to the external modulator 402. The external modulator 402 transmits / blocks the optical signal input from the light source 401 in accordance with the input electrical signal, and outputs it from the optical signal output port 406. As described above, a general high bit rate optical signal is generated.

  However, when the conventional apparatus described in FIG. 4 is used to generate a signal used for burst communication, a series of data chunks and a no-signal state existing between the next series of data chunks are created. Is difficult. The reason is that in a general external modulator driver circuit 405, in order to avoid a failure, the low frequency component of the data signal input from the electrical data signal source (data signal input port) 403 is cut off and amplified. Because. Since a signal used for burst communication including a no-signal state includes many low-frequency components, even if a signal used for burst communication is input from the electrical data signal input port 403 to the external modulator driver circuit 405, the external modulator 402 The waveform of the optical signal output from is distorted.

  For the reasons described above, there has been a problem to be solved that it is difficult to generate a signal used for burst communication when an optical signal transmission apparatus according to the prior art is used.

Chunming Qiao, “Labeled OPTICAL burst switching for IP-over-WDM integration”, IEEE Communications Magazine, vol. 38, issue 9, p. 104-114, Sep. 2000. )

  The present invention has been made to solve the above-described problems, and an object of the present invention is to generate an optical signal including no signal state suitable for applying burst communication to a photonic network system without waveform distortion. It is an object of the present invention to provide an optical signal transmission device capable of performing the above.

  In order to achieve the above object, a signal transmission device of the present invention includes a first input port for inputting a first electric signal from the outside, and a second electric signal timed with the first electric signal. Is input from the outside, and the second electric signal is a low-frequency signal by inserting a signal having a speed similar to the data signal speed between meaningful data blocks. A second input port that is a signal from which a component has been deleted; a light source that generates an optical signal, and a light source that internally includes an optical gate that switches between transmission and blocking of the optical signal by the first electrical signal; An external modulator that switches transmission / cutoff of an input optical signal from the light source according to an input voltage by the second electric signal, and an optical signal output from the external modulator is output to the outside as an output signal from the device An output port And wherein the Rukoto.

  The first electric signal may be a signal corresponding to an envelope of data transmitted from the optical signal transmission device.

  In the optical signal transmission device, the light source may be a wavelength tunable light source in which the wavelength of output light is controlled by a third electric signal input from the outside, and the optical gate may be an output signal. You may also have a function to adjust the level.

  Furthermore, in the optical signal transmitting / receiving apparatus, the light source including the optical gate may be integrated, or the light source including the optical gate and the external modulator may be integrated.

  With the above configuration, according to the present invention, an optical signal including a no-signal state suitable for applying burst communication to a photonic network system can be generated without distortion of a waveform without using a special device. An optical signal transmission device that can be realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment]
A first embodiment of an optical signal transmission apparatus according to the present invention will be described with reference to FIG. 1 includes a light source 101 that generates an optical signal, an external modulator 102, a data signal input port 103 that inputs an electrical data signal, a bias power source 104, and a driver circuit 105 for an external modulator. And an optical signal output port 106 for outputting an optical signal to the outside, and an optical gate control signal input port 109 for inputting an optical gate control signal.

  The light source 101 includes a laser 107 that generates an optical signal and an optical gate 108 that switches between transmission and blocking of the output light of the laser 107 by an optical gate control signal. Output light from the optical gate 108 is input to the external modulator 102 as output light from the light source 101.

  The electrical data signal input from the data signal input port 103 is a signal that is timed with the optical gate control signal as described in more detail below, and between the meaningful data chunks, the data This is a signal obtained by inserting a signal having the same speed as the signal speed and deleting a low-frequency signal component.

  A data signal, which is an electrical signal input from the data signal input port 103, is input to the external modulator driver circuit 105 and amplified to an appropriate desired amplitude. The amplified data signal is further supplied from the bias power source 104 to the outside. In response to the DC voltage supplied to the modulator driver circuit 105, the electric signal having an appropriate average voltage is output from the external modulator driver circuit 105. An electric signal with an appropriate average voltage output from the external modulator driver circuit 105 is input to the external modulator 102. The external modulator 102 transmits and blocks the optical signal input from the light source 101 according to the input voltage, and outputs it from the optical signal output port 106. As described above, the external modulator 102 switches transmission / cut-off of the input optical signal from the light source 101 according to the input voltage by the electrical data signal.

In the above configuration, for example, a semiconductor distributed feedback (DFB) laser can be used as the laser 107 inside the light source 101. As the optical gate 108, for example, a semiconductor optical amplifier (SOA) can be used. As the external modulator 102, for example, a modulator using a lithium niobate (LiNO ₃ ) crystal, an electroabsorption modulator using a semiconductor, or the like can be used. As the external modulator driver circuit 105, for example, a circuit in which an amplifying unit that amplifies a signal from which low-frequency components are removed and a bias circuit that adjusts an average voltage of an output signal can be used. However, these are merely examples of devices that can be used to realize the functions of the present embodiment, and cases where other devices that realize similar functions are used are also included in the present invention. In addition, the laser 107 inside the light source 101, the optical gate 108, and a part or all of the external modulator 102 may be an integrated device.

  In the present embodiment, the signal input from the electrical data signal input port 103 is a signal that includes data to be transmitted and does not have many low-frequency signal components. Only signals originally used for burst communication contain a lot of low-frequency signal components because there is no signal between a series of data chunks to be transmitted. On the other hand, a signal input from the data signal input port 103 according to the present invention has a speed comparable to the data signal speed between, for example, 1 / This is a signal obtained by reducing a low frequency signal component by inserting a zero alternating signal, a random signal, or the like.

  As described above, the electric signal from which the low-frequency signal component has been deleted is amplified without distortion in the external modulator driver circuit 105. The output signal from the external modulation path driver circuit 105 that has been amplified and adjusted to an appropriate average voltage is input to the external modulator 102, and simultaneously controls transmission and blocking of the optical signal input to the external modulator 102. .

  On the other hand, the optical gate control signal input from the optical gate control signal input port 108 is a signal corresponding to an envelope of data transmitted from the optical signal transmission apparatus. By inputting this optical gate control signal to the optical gate 108 inside the light source 101, transmission / cutoff of the optical signal output from the laser 107 is controlled. The optical signal output from the optical gate 108 is input to the external modulator 102.

  By matching the timing of the signal input from the electrical data signal input port 103 and the signal input from the optical gate control signal input port 108, the data transmitted from the external modulator driver circuit 105 to the external modulator 102 is transmitted. While the light is being input, the light source 101 can be adjusted so that the light is input to the external modulator 102. At this time, a signal generated by collecting a series of data used for burst communication can be obtained from the external modulator 102, that is, from the optical signal output port 106.

  In addition, by the above timing adjustment, in the signal component input from the electrical data signal input port 103, a series of data chunks that are meaningful data is inserted between the chunks of data, which is about the same as the data signal speed. The optical signal from the optical gate 108 is always cut off at the timing when a voltage signal of a signal component such as a 1/0 alternating signal or a random signal is input to the external modulator 102. An unintended optical signal is not output from the signal output port 106.

  By combining a plurality of general devices (or circuits, components) as described above, an optical signal including a no-signal state used for burst communication can be obtained without using a special device (or circuit, components). It is possible to realize an optical signal transmission device that can be generated without distortion.

[Second Embodiment]
Next, a second embodiment of the optical signal transmission device according to the present invention will be described with reference to FIG. The optical signal transmission device shown in FIG. 2 includes a wavelength tunable laser 201 instead of the laser 107 in FIG. 1 and newly includes a wavelength tunable laser control device 202 and an output wavelength control signal input port 203. Other components are the same as those in the first embodiment.

  In the above configuration, as the wavelength tunable laser 201, for example, the output of a laser whose output wavelength can be set to a desired wavelength by controlling the element temperature of a semiconductor DFB laser or a plurality of DFB lasers having different emission wavelengths is output. A laser that can be set to a desired wavelength by driving only a DFB laser that is coupled by an optical coupler and emits light at a desired output wavelength, and the refractive index of the element is adjusted by injecting current, and output. A multi-terminal type semiconductor laser that can set the wavelength to a desired wavelength can be used. However, these wavelength tunable lasers are merely examples of devices that can be used to realize the functions of the present embodiment, and cases where other devices that realize similar functions are used are also included in the present invention.

  In the present embodiment, the wavelength tunable laser 201 is built in the light source 101. The output wavelength of the wavelength tunable laser 201 is controlled by the wavelength tunable laser control device 202 in accordance with a signal input from the output wavelength control signal input port 203, and is set to a desired wavelength.

  Since the configuration other than the above is the same as that of the first embodiment, a detailed description thereof will be omitted.

  In the present embodiment, by using the tunable laser 201 described above, it is possible to output a signal generated as a series of data used for burst communication at a different signal wavelength for each series of data chunks. An optical signal transmission device can be obtained.

  As in the first embodiment, it is possible to realize an optical signal transmission device that can generate an optical signal including a no-signal state used for burst communication without using waveform distortion without using a special device. It is.

[Third Embodiment]
Furthermore, a third embodiment of the optical signal transmission device according to the present invention will be described with reference to FIG. The optical signal transmission device shown in FIG. 3 newly includes an optical gate control device 301 in addition to the components shown in FIG. Other components are the same as those in the second embodiment.

  In this embodiment, a countermeasure is shown when the output level of the wavelength tunable laser 201 varies for each output wavelength. The output wavelength of the wavelength tunable laser 201 is controlled by the wavelength tunable laser control device 202 in accordance with a signal (output wavelength control signal) input from the output wavelength control signal input port 203, and is set to a desired wavelength. At the same time, a signal input from the output wavelength control signal input port 203 (output wavelength control signal) and a signal input from the optical gate control signal input port 108 (optical gate control signal) are respectively optical gate control devices 301. Is input. The optical gate control device 301 controls transmission / cut-off of the optical gate 107 according to the signal input from the optical gate control signal input port 108 and outputs light according to the signal input from the output wavelength control signal input port 203. By controlling the output level from the gate 107, output light from the light source 101 is obtained at a desired output timing and output level.

  For example, when SOA is used as the optical gate 108, the gain is controlled by the amount of injected current, so that the optical gate control device 301 has a time corresponding to a signal input from the optical gate control signal input port 108. A current amount corresponding to the signal input from the output wavelength control signal input port 203 is injected into the optical gate 107. Thereby, output light is obtained from the optical gate 107 at a desired output timing and output level.

  Since the configuration other than the above is the same as that of the first and second embodiments, a detailed description thereof will be omitted.

  In this embodiment, by using the optical gate control device 301 as described above, a signal generated as a series of data used for burst communication is output at a different signal wavelength for each series of data chunks. And an optical signal transmission device with a uniform output level.

  It is to be noted that the first and second embodiments can realize an optical signal transmission device that can generate an optical signal including a no-signal state used for burst communication without using waveform distortion without using a special device. It is the same as the form.

[Other embodiments]
In the above, the preferred embodiment of the present invention has been described by way of example. However, the embodiment of the present invention is not limited to the above-described example, and the constituent members thereof are within the scope of the claims. Various modifications such as replacement, change, addition, increase / decrease in number, change in shape design, and the like are all included in the embodiment of the present invention.

It is a block diagram which shows the structure of the optical signal transmitter which is the 1st Embodiment of this invention. It is a block diagram which shows the structure of the optical signal transmitter which is the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the optical signal transmitter which is the 3rd Embodiment of this invention. It is a block diagram which shows the structural example of the conventional optical signal transmitter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Light source 102 External modulator 103 Electrical data signal input port 104 Bias power supply 105 Driver circuit for external modulator 106 Optical signal output port 107 Laser 108 Optical gate 109 Optical gate control signal input port 201 Wavelength variable laser 202 Wavelength variable laser control device 203 Output wavelength control signal input port 301 Optical gate control device 401 Light source 402 External modulator 403 Electrical data signal input port 404 Bias power supply 405 Driver circuit for external modulator 406 Optical signal output port

Claims (5)

A first input port for inputting a first electrical signal from the outside;
A second input port for inputting a second electrical signal, which is timed with the first electrical signal, from the outside, wherein the second electrical signal is a data block between meaningful chunks of data; A second input port, which is a signal obtained by inserting a signal having a speed similar to the signal speed and deleting a low-frequency signal component;
A light source that generates an optical signal, the optical source having an optical gate that switches between transmission and blocking of the optical signal by the first electric signal;
An external modulator that switches transmission / cutoff of an input optical signal from the light source in accordance with an input voltage by the second electric signal;
An output port for outputting an optical signal output from the external modulator to the outside as an output signal from the device;
An optical signal transmission device comprising:   The optical signal transmission device according to claim 1, wherein the first electric signal is a signal corresponding to an envelope of data transmitted from the optical signal transmission device.   3. The optical signal transmission device according to claim 1, wherein the light source is a wavelength tunable light source in which a wavelength of output light is controlled by a third electrical signal input from the outside.   4. The optical signal transmission apparatus according to claim 1, wherein the optical gate has a function of adjusting a level of an output signal. 5. The light source including the optical gate is integrated as a single unit, or the light source including the optical gate and the external modulator are integrated as a single unit. The optical signal transmission device described.

Images