JP2014138195A - Wavelength-tunable burst transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength-tunable burst transmitter achieving increased output of transmission output and improvement in signal light leakage when a burst optical signal is off.SOLUTION: The present invention relates to a wavelength-tunable burst transmitter including: a wavelength-tunable transmitter for modulating light with a data signal to output continuous optical signals, the light having a wavelength determined by a wavelength switching signal; and a burst control section for amplifying or blocking the continuous optical signals from the wavelength-tunable transmitter for each burst frame by a burst control signal.

Description

  The present invention relates to increasing the output of a wavelength tunable burst transmitter.

  In recent years, the Passive Optical Network (PON) system has been introduced all over the world as an optical access system supporting the Fiber To The Home (FTTH) service, which has been rapidly spreading.

  The PON system is installed in a plurality of subscriber homes with respect to one terminal device (OLT: Optical Line Terminal) installed in the accommodation station via an optical splitter installed in the optical fiber transmission line. An optical access system that can accommodate an optical network unit (ONU) and share optical fiber transmission lines, optical splitters, and OLTs among multiple subscribers. is there.

  At present, in Japan, a GE-PON (Gigabit Ethernet-PON) (Ethernet is a registered trademark) system having a transmission amount of 1 Gb / s is mainly introduced commercially. Further, research and development of 10G-EPON having a total transmission capacity of 10 Gb / s class as a next-generation optical access system that realizes further speeding up is underway.

  Then, the next generation optical access system aimed at further speeding up and sophistication of the optical access system has been studied, and WDM (Wavelength Division Multiplexing) as XG-PON2 in FSAN (Full Service Access Network) which is a standardization organization. ) -TDM (Time Division Multiplexing) PON system standardization started in 2012.

  These WDM / TDM-PON systems perform wavelength-axis multiplexing (WDM) using the characteristics of light in addition to time-axis multiplexing (TDM) that has been used in previous PON systems. It is possible to increase the efficiency of access network and maintenance management, and it can be expected to increase the flexibility of the access network.

  In addition, a dramatic increase in transmission capacity can be expected by applying WDM technology. This system has a large capacity of the system by providing wavelength tunability to the terminating device (LC: Line Card) installed in the accommodation station and the transmitter / receiver built in the ONU, and making effective use of the time axis and wavelength axis. Realize both optimization and flexibility. In order to realize these WDM / TDM-PON systems, a wavelength variable burst transmitter capable of high-speed wavelength switching and burst operation is required.

  As a wavelength tunable light source, a laser array in which lasers with different oscillation wavelengths are integrated, a distributed Bragg reflection laser (DBR: Distributed Bragg Reflector Laser), an external cavity laser (ECL: External Cavity Laser), etc. that changes the oscillation wavelength of the laser A wavelength tunable burst transmitter using this is being studied.

Hirotaka Nakamura et al, “40 Gbit / s λ-tunable stacked-WDM / TDM-PON using dynamic wavelength and bandwidth width allocation”, OThT4, OSA / OFC / NFOE11 201.

  In order to construct a flexible and efficient access network using the WDM / TDM-PON system, the service provision area can be expanded by extending the transmission distance, and the accommodation efficiency can be increased by expanding the number of branches of splitters and AWGs (Arrayed Waveguide Gratings). Improvement is essential.

  In order to realize these transmission distances and expansion of the number of branches, it is necessary to improve the loss budget of the system, and application of repeater optical amplifiers, higher output of transmitters, and improvement of receiver reception sensitivity are effective. It is.

  While the repeater optical amplifier has a large loss budget expansion effect, it is necessary to install a device in an outdoor transmission line, and environmental resistance and reliability are problems. In addition, to improve the receiver sensitivity, it is necessary to study from the device level in order to achieve higher sensitivity of the photodiode itself, and the characteristics of the PON system that achieves economy by using general-purpose products In view of this, it is not a realistic method.

  In addition, the method of using an optical amplifier as a preamplifier for high sensitivity requires a narrow band-pass filter that eliminates the influence of spontaneous emitted light (ASE) emitted from the optical amplifier. It is difficult to apply to a PON system where the oscillation wavelength varies greatly due to temperature, individual differences, and the like.

  As a wavelength tunable light source, a laser array in which lasers with different oscillation wavelengths are integrated, a distributed Bragg reflection laser (DBR: Distributed Bragg Reflector Laser), an external cavity laser (ECL), etc. that changes the oscillation wavelength of the laser A wavelength tunable burst transmitter using the above has been studied (for example, see Non-Patent Document 1).

  On the other hand, the increase in transmitter output power can be improved by several dB by improving the coupling efficiency between the LD and the optical fiber. Further, by combining an optical amplifier with a transmitter as a booster amplifier, output power exceeding 10 dBm can be easily obtained.

  In addition, by using an electroabsorption (EA) modulator or the like as an external modulator, the transmitter can increase the system transmission speed and improve dispersion tolerance during long-distance transmission. / TDM-PON system required for long extension and multi-branching.

  On the other hand, a transmitter configuration using an external modulator such as an EA modulator has a problem that it is difficult to increase the output because the insertion loss of the external modulator itself is large. Furthermore, since light leaks from the external modulator when the burst optical signal is OFF, it is necessary to stop the light emission of the light source itself when the burst optical signal is OFF, and an external modulator and a burst transmitter are required.

  An object of the present invention is to provide a wavelength tunable burst transmitter that realizes high transmission output and improvement in signal light leakage when the burst optical signal is OFF.

  Therefore, the present invention is a tunable burst transmitter that blocks light when the burst optical signal is OFF.

  Specifically, the present invention provides a wavelength tunable transmitter that modulates light of a wavelength determined by a wavelength switching signal with a data signal and outputs a continuous optical signal, and the wavelength tunable for each burst frame by a burst control signal. And a burst control unit that amplifies or blocks a continuous optical signal from the transmitter.

  Further, the present invention is the above invention, wherein the wavelength tunable transmitter directly modulates light having a wavelength determined by a wavelength switching signal with the data signal, and bursts the light with a burst generation signal synchronized with the burst control signal. The burst control unit outputs a burst optical signal, and the burst control unit is configured by a semiconductor optical amplifier (SOA), amplifies the burst optical signal when turned on by the burst control signal, and absorbs the burst optical signal when turned off. This is a wavelength tunable burst transmitter.

  Further, the present invention is the above invention, wherein the wavelength tunable transmitter directly modulates light of a wavelength determined by a wavelength switching signal with the data signal and outputs a continuous optical signal, and the burst control unit is a semiconductor A wavelength tunable burst transmitter comprising an optical amplifying element (SOA: Semiconductor Optical Amplifier), which amplifies a continuous optical signal when ON by the burst control signal and absorbs the continuous optical signal when OFF.

  Further, the present invention provides the wavelength variable transmitter according to the above invention, wherein the wavelength tunable transmitter bursts light of a wavelength determined by a wavelength switching signal with a burst generation signal synchronized with the burst control signal and outputs burst light. A light source and an external modulator that modulates burst light from the wavelength tunable light source with a data signal and outputs a burst optical signal, and the burst control unit is a semiconductor optical amplifier (SOA). A wavelength tunable burst transmitter configured to amplify the burst optical signal when turned on by the burst control signal and absorb the burst optical signal when turned off.

  Further, in the present invention according to the above invention, the wavelength tunable transmitter continuously outputs a wavelength tunable light source that outputs light having a wavelength determined by a wavelength switching signal, and light from the wavelength tunable light source is modulated with a data signal. An external modulator that outputs an optical signal, and the burst control unit is composed of a semiconductor optical amplifier (SOA), amplifies the continuous optical signal when turned on by the burst control signal, and is turned off. A tunable burst transmitter characterized in that it sometimes absorbs the continuous optical signal.

  Further, the present invention provides the wavelength variable transmitter according to the above invention, wherein the wavelength tunable transmitter bursts light of a wavelength determined by a wavelength switching signal with a burst generation signal synchronized with the burst control signal and outputs burst light. A light source, and an external modulator that modulates burst light from the wavelength tunable light source with a data signal and outputs a burst optical signal, and the burst control unit optically amplifies the burst optical signal; A variable wavelength burst transmitter comprising: a variable attenuator that transmits a burst optical signal when ON by the burst control signal and blocks the burst optical signal when OFF.

  Further, in the present invention according to the above invention, the wavelength tunable transmitter continuously outputs a wavelength tunable light source that outputs light having a wavelength determined by a wavelength switching signal, and light from the wavelength tunable light source is modulated with a data signal. An external modulator that outputs an optical signal, the burst control unit optically amplifies the continuous optical signal, and transmits the continuous optical signal when turned on by the burst control signal, and the continuous optical signal when turned off And a variable attenuating unit that blocks the wavelength tunable burst transmitter.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the wavelength variable burst transmitter which implement | achieved the high output of a transmission output, and the improvement of the signal light leakage at the time of a burst signal OFF.

Configuration example of wavelength tunable burst transmitter of the present invention Configuration example of wavelength tunable burst transmitter of the present invention Example of operation of wavelength tunable burst transmitter of the present invention Configuration example of wavelength tunable burst transmitter of the present invention Example of operation of wavelength tunable burst transmitter of the present invention Configuration example of wavelength tunable burst transmitter of the present invention Configuration example of wavelength tunable burst transmitter of the present invention Configuration example of wavelength tunable burst transmitter of the present invention Example of operation of wavelength tunable burst transmitter of the present invention Configuration example of wavelength tunable burst transmitter of the present invention Example of operation of wavelength tunable burst transmitter of the present invention

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
The wavelength variable burst transmitter according to the first embodiment will be described with reference to FIG. The wavelength tunable burst transmitter 10 of the present embodiment includes a wavelength tunable transmitter 11 that modulates light of a wavelength determined by a wavelength switching signal with a data signal and outputs a continuous optical signal, and a burst control signal for each burst frame. And a burst control unit 12 for amplifying or blocking the continuous optical signal from the wavelength tunable transmitter 11.

  The wavelength switching signal determines the oscillation wavelength of the wavelength tunable transmitter 11. The data signal directly modulates the output of the wavelength tunable transmitter 11 or modulates it with an external modulator. The burst control signal is controlled by the burst control unit 12 so as to amplify or block the optical signal.

  The variable wavelength transmitter 11 includes a laser array in which a plurality of lasers having a fixed oscillation wavelength are integrated, a DBR laser in which the transmission wavelength of the laser itself changes, an ECL, and the like. The wavelength switching signal is used to switch the oscillation wavelength of the wavelength variable transmitter 11 and determines the oscillation wavelength for each burst signal frame. With these operations, the wavelength variable transmitter 11 outputs a signal having an arbitrary wavelength.

  The signal output from the wavelength tunable transmitter 11 is input to the burst control unit 12. The burst control signal determines the state of the burst signal generated by the burst control unit 12. The burst control unit 12 generates a burst optical signal by performing amplification for each burst frame when the burst control signal is ON and blocking for each burst frame when the burst control signal is OFF.

  The wavelength variable transmitter 11 is assumed to be a direct modulation system or an external modulation system. In the case of the direct modulation method, light is directly modulated by a data signal. In the case of an external modulation system, light is modulated by a data signal by an external modulator.

  Since the external modulator has a large insertion loss, it is difficult to increase the output of the output signal of the external modulator in the case of the external modulation system. In order to solve these problems, this configuration can realize a high output of +10 dBm or more by installing an optical amplifier as a burst control unit and using it as a booster amplifier. Since the burst control unit optically amplifies only when the burst control signal is ON, it becomes possible to compensate for the insertion loss received by the external modulator at the output of the variable wavelength transmitter.

  On the other hand, the external modulator has a problem that light leaks when the burst signal is OFF. In the PON system, a plurality of ONUs are connected to one OLT because of the network configuration. For this reason, if even a slight amount of light leaks at the time of burst OFF built in the ONU, the leakage light for a plurality of ONUs is added and input to the OLT as a large leakage light power. Due to these effects, there is a risk of power penalties occurring in the reception characteristics of the OLT, failure of the OLT receiver due to excessive input to the OLT, and the leakage light when the burst signal is OFF is completely blocked. Has become an issue.

  For this reason, in this embodiment, when the burst optical signal of the variable wavelength burst transmitter is OFF, the burst optical signal is blocked by the burst control unit. Thereby, the burst optical signal leaking from the external modulator when the burst optical signal is OFF can be blocked.

  With this operation, in the light emission state where the burst optical signal is ON, the output of the wavelength variable burst transmitter is increased, and in the extinction state where the burst optical signal is OFF, the weak burst optical signal leaking from the wavelength variable burst transmitter Can be shut off.

  In the wavelength tunable burst transmitter of the present embodiment, high output when the burst optical signal is ON, and leakage light when the burst optical signal is OFF can be reduced, and a good extinction ratio can be obtained.

(Embodiment 2)
The wavelength variable burst transmitter according to the second embodiment will be described with reference to FIG. The variable wavelength burst transmitter 10 of this embodiment includes a variable wavelength transmitter and a burst control unit. The wavelength tunable transmitter 11 directly modulates light having a wavelength determined by the wavelength switching signal with a data signal, and outputs a burst optical signal bursted by a burst generation signal synchronized with the burst control signal. A semiconductor optical amplifier (SOA) as a burst controller amplifies or blocks a burst optical signal from the wavelength variable transmitter 11 for each burst frame by a burst control signal. The SOA driver 122 controls the drive current of the SOA 121 for each burst frame. The SOA 121 amplifies the burst optical signal when the burst control signal is ON, and absorbs the burst optical signal when the burst control signal is OFF.

  The variable wavelength transmitter 11 includes a laser array in which a plurality of lasers having a fixed oscillation wavelength are integrated, a DBR laser in which the transmission wavelength of the laser itself changes, an ECL, and the like. The wavelength switching signal is used to switch the oscillation wavelength of the wavelength tunable transmitter 11, and the oscillation wavelength can be determined for each burst signal frame. The burst signal generation signal determines the ON or OFF state of the burst optical signal output from the wavelength tunable transmitter 11, and determines the burst state for each burst signal frame.

  In this embodiment, the light generated by the wavelength tunable transmitter 11 is directly modulated with a data signal, and bursted with a burst generation signal to generate a burst optical signal. With these operations, the variable wavelength transmitter 11 outputs a burst optical signal having an arbitrary wavelength for each burst signal frame.

  The burst optical signal output from the wavelength tunable transmitter 11 is input to the SOA 121 serving as a burst control unit. The SOA 121 is used as a booster amplifier installed at the output stage of the wavelength tunable burst transmitter. For this reason, the SOA 121 output can obtain a high output power of +10 dBm or more, and in addition, the high output of the wavelength tunable burst transmitter 10 can be obtained by combining with the wavelength tunable transmitter 11 of the direct modulation method without the insertion loss due to the external modulator. Can be realized.

  The burst generation signal and the burst control signal are in a synchronized state. When the burst light from the wavelength tunable transmitter 11 is ON, the burst control signal is turned ON, the drive current is applied from the SOA driver 122 to the SOA 121, and the burst optical signal is amplified. When the burst light from the wavelength tunable transmitter 11 is OFF, the burst control signal is turned OFF, the drive current of the SOA driver 122 is lowered, and the SOA 121 is operated in the absorption region. As a result, the SOA 121 functions as an absorbing medium that absorbs light, and can block light when the burst optical signal is OFF.

  FIG. 3 shows the relationship between the output of the wavelength tunable transmitter 11, the burst control signal, and the output of the SOA 121. When the wavelength tunable transmitter 11 is outputting a burst optical signal, the burst control signal is turned on and the drive current is increased, thereby increasing the gain of the SOA 121 and using it as an amplification medium. As a result, the burst optical signal is optically amplified by the SOA 121 to increase the output. When the wavelength tunable transmitter 11 is not outputting a burst optical signal, the SOA 121 is used as an absorbing medium by turning off the burst control signal and lowering the drive current.

  With this operation, in the light emission state where the burst optical signal is ON, the output of the wavelength variable burst transmitter is increased, and in the extinction state where the burst optical signal is OFF, the weak burst optical signal leaking from the wavelength variable burst transmitter As a result, the burst optical signal having a good extinction ratio can be generated.

  The wavelength tunable burst transmitter of the present embodiment can increase the output when the burst optical signal is ON, reduce the leakage light when the burst optical signal is OFF, and achieve a good extinction ratio.

(Embodiment 3)
The wavelength variable burst transmitter according to the third embodiment will be described with reference to FIG. The variable wavelength burst transmitter 10 of this embodiment includes a variable wavelength transmitter and a burst control unit. The wavelength tunable transmitter 11 directly modulates light having a wavelength determined by the wavelength switching signal with a data signal, and outputs a continuous optical signal. As a burst controller, a semiconductor optical amplifier (SOA) as a burst controller amplifies or blocks the burst optical signal from the wavelength tunable transmitter 11 for each burst frame by the burst control signal. The SOA driver 122 controls the drive current of the SOA 121 for each burst frame. The SOA 121 amplifies the burst optical signal when the burst control signal is ON, and absorbs the burst optical signal when the burst control signal is OFF.

  In the present embodiment, the variable wavelength transmitter 11 generates a continuous optical signal by directly modulating light with a data signal. The variable wavelength transmitter 11 includes a laser array in which a plurality of lasers having a fixed oscillation wavelength are integrated, a DBR laser in which the transmission wavelength of the laser itself changes, an ECL, and the like. The wavelength switching signal is used to switch the oscillation wavelength of the wavelength variable transmitter 11 and determines the oscillation wavelength for each burst signal frame. The SOA 121 is used as a booster amplifier installed at the output stage of the wavelength tunable burst transmitter 11.

  With these operations, the wavelength tunable transmitter 11 outputs a continuous optical signal having an arbitrary wavelength. The continuous optical signal output from the wavelength tunable transmitter 11 is input to the SOA 121. For this reason, the SOA 121 output can obtain a high output power of +10 dBm or more, and in addition, the high output of the wavelength tunable burst transmitter 10 can be obtained by combining with the wavelength tunable transmitter 11 of the direct modulation method without the insertion loss due to the external modulator. Can be realized.

  The SOA 121 applies a drive current from the SOA driver 122 to the SOA when the burst control signal is ON, and amplifies the continuous optical signal. When the burst control signal is OFF, the drive current of the SOA driver 122 is lowered to operate the SOA in the absorption region. As a result, the SOA 121 functions as an absorption medium that absorbs light, and the continuous optical signal is blocked and a burst optical signal is generated.

  FIG. 5 shows the relationship between the output of the wavelength tunable transmitter 11, the burst control signal, and the output of the SOA 121. The variable wavelength transmitter 11 always outputs a continuous optical signal. When the burst control signal is turned ON, the gain of the SOA 121 is increased by increasing the drive current to the SOA 121, and the SOA 121 is used as an amplification medium. When the burst control signal is OFF, the SOA 121 is used as an absorbing medium by reducing the drive current to the SOA 121. As a result, the continuous optical signal is blocked by the SOA 121, and a burst optical signal is generated.

  The wavelength tunable burst transmitter of the present embodiment can increase the output when the burst optical signal is ON, reduce the leakage light when the burst optical signal is OFF, and achieve a good extinction ratio. In addition, this configuration does not require the use of a burst-compatible wavelength variable transmitter, and simplification of the configuration and economic improvement of the apparatus can be expected.

(Embodiment 4)
A wavelength variable burst transmitter according to the fourth embodiment will be described with reference to FIG. The variable wavelength burst transmitter 10 of this embodiment includes a variable wavelength transmitter and a burst control unit. The wavelength tunable transmitter includes a wavelength tunable light source 111 that bursts light having a wavelength determined by a wavelength switching signal with a burst generation signal synchronized with the burst control signal and outputs burst light, and burst light from the wavelength tunable light source 111. And an external modulator 112 that modulates the data with a data signal and outputs a burst optical signal. As a burst controller, a semiconductor optical amplifier (SOA) as a burst controller amplifies or blocks the burst optical signal from the wavelength tunable transmitter 11 for each burst frame by the burst control signal. The SOA driver 122 controls the drive current of the SOA 121 for each burst frame. The external modulator driver 113 drives the external modulator 112.

  The wavelength tunable light source 111 includes a laser array in which a plurality of lasers having a fixed oscillation wavelength are integrated, a DBR laser in which the transmission wavelength of the laser itself changes, an ECL, and the like. The external modulator 112 can be expected to increase the signal speed and improve dispersion tolerance by using an EA modulator or an LN modulator. The wavelength switching signal is used to switch the oscillation wavelength of the wavelength tunable light source 111, and determines the oscillation wavelength for each burst signal frame. The burst light output from the wavelength variable light source 111 is modulated with a data signal by the external modulator 112, and a burst optical signal is output.

  The SOA 121 is used as a booster amplifier installed at the output stage of the wavelength tunable burst transmitter 10. For this reason, the SOA 121 output can be increased to +10 dBm or more by compensating for the insertion loss due to the external modulator and further amplifying it.

  The burst generation signal and the burst control signal are in a synchronized state. When the burst optical signal from the external modulator 112 is ON, the burst control signal is turned ON, the drive current is applied from the SOA driver 122 to the SOA 121, and the burst optical signal is amplified. When the burst optical signal from the external modulator 112 is OFF, the burst control signal is turned OFF, the drive current of the SOA driver 122 is lowered, and the SOA 121 is operated in the absorption region. As a result, when the SOA 121 functions as an absorbing medium that absorbs light, a burst optical signal in which leakage light is blocked is output. The operation of the wavelength tunable burst transmitter of this embodiment is the same as that shown in FIG.

  Therefore, it is possible to increase the output of the wavelength tunable burst transmitter by compensating the output of the wavelength tunable light source, which has been reduced by the insertion loss of the external modulator 112, and further amplifying it as a booster amplifier.

  The wavelength tunable burst transmitter of the present embodiment can increase the output when the burst optical signal is ON, reduce the leakage light when the burst optical signal is OFF, and achieve a good extinction ratio.

(Embodiment 5)
A wavelength tunable burst transmitter according to the fifth embodiment will be described with reference to FIG. The wavelength tunable burst transmitter of this embodiment includes a wavelength tunable transmitter and a burst control unit. The wavelength tunable transmitter includes a wavelength tunable light source 111 that outputs light having a wavelength determined by a wavelength switching signal, and an external modulator 112 that modulates light from the wavelength tunable light source 111 with a data signal and outputs a continuous optical signal; . As a burst controller, a semiconductor optical amplifier (SOA) as a burst controller amplifies or blocks the burst optical signal from the wavelength tunable transmitter 11 for each burst frame by the burst control signal. The external modulator driver 113 drives the external modulator 112. The SOA driver 122 controls the drive current of the SOA 121 for each burst frame.

  The wavelength tunable light source 111 includes a laser array in which a plurality of lasers having a fixed oscillation wavelength are integrated, a DBR laser in which the transmission wavelength of the laser itself changes, an ECL, and the like. The external modulator 112 can be expected to increase the signal speed and improve the dispersion tolerance by using an EA modulator or an LN modulator.

  The wavelength switching signal is used to switch the oscillation wavelength of the wavelength tunable light source 111, and the oscillation wavelength can be determined for each burst signal frame. In this embodiment, the light output from the wavelength tunable light source 111 is modulated with a data signal by the external modulator 112 to generate a continuous optical signal. By these operations, the wavelength tunable transmitter outputs a continuous optical signal having an arbitrary wavelength. The operation of the wavelength tunable burst transmitter of this embodiment is the same as that shown in FIG.

  The SOA 121 is used as a booster amplifier installed at the output stage of the wavelength tunable burst transmitter 10. For this reason, the SOA 121 output can be increased to +10 dBm or more by compensating for the insertion loss due to the external modulator and further amplifying it.

  The SOA 121 applies an SOA driver 122 drive current when the burst control signal is ON, and amplifies the continuous optical signal. When the burst control signal is OFF, the drive current of the SOA driver 122 is lowered to operate the SOA 121 in the absorption region. As a result, the SOA 121 functions as an absorption medium that absorbs light, and the continuous optical signal is blocked and a burst optical signal is generated.

  The wavelength tunable burst transmitter of the present embodiment can increase the output when the burst optical signal is ON, reduce the leakage light when the burst optical signal is OFF, and achieve a good extinction ratio. Further, it is not necessary to use a burst-compatible wavelength tunable transmitter, so that simplification of the configuration and economy of the apparatus can be expected.

(Embodiment 6)
A wavelength tunable burst transmitter according to the sixth embodiment will be described with reference to FIG. The variable wavelength burst transmitter of this embodiment includes a variable wavelength transmitter and a burst control unit. The wavelength tunable transmitter includes a wavelength tunable light source 111 that bursts light having a wavelength determined by the wavelength switching signal with a burst generation signal synchronized with the burst control signal and outputs burst light, and burst light from the wavelength tunable light source 111. An external modulator 112 that modulates with a data signal and outputs a burst optical signal. The burst control unit optically amplifies the burst optical signal from the external modulator 112, and transmits the burst optical signal from the optical amplifier 123 when turned on by the burst control signal, and burst light from the optical amplifier 123 when turned off. And a variable attenuator 124 that blocks the signal. The external modulator driver 113 drives the external modulator 112. The variable attenuating unit driver 125 controls the variable attenuating unit 124 at high speed for each burst frame using a burst control signal.

  The wavelength tunable light source 111 includes a laser array in which a plurality of lasers having a fixed oscillation wavelength are integrated, a DBR laser in which the transmission wavelength of the laser itself changes, an ECL, and the like. The external modulator 112 can be expected to increase the signal speed and improve the dispersion tolerance by using an EA modulator or an LN modulator. Although the external modulator 112 is provided here, the variable wavelength light source 111 may directly modulate the burst light with a data signal.

  The wavelength switching signal is used to switch the oscillation wavelength of the wavelength tunable light source 111, and determines the oscillation wavelength for each burst signal frame. The burst light output from the wavelength tunable light source 111 is modulated with a data signal by the external modulator 112 and input to the optical amplifier 123 as a burst optical signal. The optical amplifier 123 is used as a booster amplifier installed at the output stage of the wavelength tunable burst transmitter 10. Therefore, the output of the wavelength tunable burst transmitter 10 can be increased by compensating the output of the wavelength tunable light source 111 that has been reduced by the insertion loss of the external modulator 112 and further amplifying it as a booster amplifier.

  The burst generation signal and the burst control signal are in a synchronized state. The burst optical signal amplified by the optical amplifier 123 is input to the variable attenuation unit 124. When the burst optical signal from the optical amplifier 123 is ON, the burst control signal is turned ON, and the attenuation value of the variable attenuation unit 124 is controlled to be low. As a result, the burst optical signal is output from the variable attenuator 124 with only a slight insertion loss, and the output of the wavelength variable burst transmitter 10 is increased.

  When the burst optical signal from the optical amplifier 123 is OFF, the burst control signal is turned OFF, and the attenuation value of the variable attenuation unit 124 is controlled to be high. Thus, the burst optical signal is greatly attenuated by the variable attenuating unit 124, and the output of the wavelength tunable burst transmitter 10 output from the variable attenuating unit 124 is cut off.

  FIG. 9 shows the relationship between the output of the wavelength tunable light source 111, the loss value of the variable attenuation unit 124, and the output of the variable attenuation unit 124. When the wavelength tunable light source 111 outputs burst light, the burst optical signal is output only by receiving insertion loss of the variable attenuator by lowering the loss value of the variable attenuator 124. As a result, the output when the burst optical signal is ON is a signal with a high output by the optical amplifier.

  When the wavelength tunable light source 111 is not outputting burst light, the loss value of the variable attenuator 124 is increased to block the burst light signal. As a result, the output when the burst light signal is OFF is blocked by the variable attenuating unit 124, and leakage light is reduced.

  The wavelength tunable burst transmitter of the present embodiment can increase the output when the burst optical signal is ON, reduce the leakage light when the burst optical signal is OFF, and achieve a good extinction ratio.

(Embodiment 7)
A wavelength tunable burst transmitter according to the seventh embodiment will be described with reference to FIG. The wavelength tunable burst transmitter of this embodiment includes a wavelength tunable transmitter and a burst control unit. The wavelength tunable transmitter includes a wavelength tunable light source 111 that outputs light having a wavelength determined by a wavelength switching signal, and an external modulator 112 that modulates light from the wavelength tunable light source 111 with a data signal and outputs a continuous optical signal; . The burst control unit optically amplifies the continuous optical signal from the external modulator 112, and transmits the continuous optical signal from the optical amplifier 123 when turned on by the burst control signal, and the continuous light from the optical amplifier 123 when turned off. And a variable attenuator 124 that blocks the signal. The external modulator driver 113 controls the external modulator 112 at high speed for each burst frame. The variable attenuating unit driver 125 controls the variable attenuating unit 124 at high speed for each burst frame using a burst control signal.

  The wavelength switching signal is used to switch the oscillation wavelength of the wavelength tunable light source 111, and determines the oscillation wavelength for each burst signal frame. The burst control signal controls the variable attenuator driver 125.

  The wavelength tunable light source 111 includes a laser array in which a plurality of lasers having a fixed oscillation wavelength are integrated, a DBR laser in which the transmission wavelength of the laser itself changes, an ECL, and the like. The external modulator 112 can be expected to increase the signal speed and improve the dispersion tolerance by using an EA modulator or an LN modulator. In the present embodiment, the light output from the wavelength tunable light source 111 is modulated by the external modulator 112 to generate a continuous optical signal. The wavelength tunable light source 111 directly modulates the light with a data signal. May be.

  The optical amplifier 123 is used as a booster amplifier installed at the output stage of the wavelength tunable burst transmitter 10. For this reason, the output of the wavelength tunable burst transmitter 10 can be increased by compensating for the output of the wavelength tunable light source 111 that has been reduced by the insertion loss of the external modulator 112 and further amplifying it as a booster amplifier.

  The continuous optical signal amplified by the optical amplifier 123 is input to the variable attenuation unit 124. When the continuous optical signal is input to the variable attenuation unit 124, the attenuation value of the variable attenuation unit 124 with respect to the continuous optical signal is controlled to be low when the burst control signal is ON. As a result, when the burst of the continuous optical signal is turned on, only a slight insertion loss is received and output from the variable attenuating unit 124, so that the output of the wavelength variable burst transmitter 10 is increased.

  On the other hand, when the burst control signal is OFF, the attenuation value of the variable attenuation 124 is controlled to be high. Thereby, when the burst of the continuous optical signal is turned off, a large attenuation is received, and the output from the variable attenuation unit 124 is cut off. Compared with the sixth embodiment, this configuration does not require the use of a variable wavelength light source corresponding to a burst for the transmitter, and simplification of the configuration and economic improvement of the apparatus can be expected.

  FIG. 11 shows the relationship between the output of the wavelength variable light source 111, the loss value of the variable attenuation unit 124, and the output of the variable attenuation unit 124. The variable wavelength light source 111 always outputs light continuously. At this time, the burst ON signal is generated by lowering the loss value of the variable attenuator 124 for the burst ON portion of the continuous optical signal. For the burst OFF part of the continuous optical signal, the burst OFF signal is generated by increasing the loss value of the variable attenuator 124.

  The wavelength tunable burst transmitter of the present embodiment can increase the output when the burst optical signal is ON, reduce the leakage light when the burst optical signal is OFF, and achieve a good extinction ratio.

  The wavelength tunable burst transmitter according to the present invention can be applied to WDM / TDM-PON because it can solve the problems of high output when burst is ON and improvement of leakage light when burst is OFF.

10: Wavelength variable burst transmitter 11: Wavelength variable transmitter 111: Wavelength variable light source 112: External modulator 113: External modulator driver 12: Burst controller 121: Semiconductor optical amplifier 122: Semiconductor optical amplifier driver 123: Optical amplifier 124 : Variable attenuation unit 125: Variable attenuation unit driver

Claims (7)

A wavelength tunable transmitter that modulates light of a wavelength determined by a wavelength switching signal with a data signal and outputs a continuous optical signal;
A tunable burst transmitter, comprising: a burst control unit that amplifies or blocks a continuous optical signal from the tunable transmitter for each burst frame by a burst control signal. The wavelength tunable transmitter directly modulates light of a wavelength determined by a wavelength switching signal with the data signal, and outputs a burst optical signal burst by a burst generation signal synchronized with the burst control signal,
The burst control unit includes a semiconductor optical amplifier (SOA), amplifies the burst optical signal when the burst control signal is turned on, and absorbs the burst optical signal when turned off. 2. The wavelength tunable burst transmitter according to 1. The wavelength tunable transmitter directly modulates light of a wavelength determined by a wavelength switching signal with the data signal and outputs a continuous optical signal,
The burst control unit includes a semiconductor optical amplifier (SOA), amplifies a continuous optical signal when the burst control signal is turned on, and absorbs the continuous optical signal when turned off. 2. The wavelength tunable burst transmitter according to 1. The wavelength tunable transmitter includes: a wavelength tunable light source that bursts light having a wavelength determined by a wavelength switching signal with a burst generation signal synchronized with the burst control signal and outputs burst light; and a burst from the wavelength tunable light source. An external modulator that modulates light with a data signal and outputs a burst optical signal,
The burst control unit is composed of a semiconductor optical amplifier (SOA), and amplifies the burst optical signal when ON by the burst control signal and absorbs the burst optical signal when OFF. The tunable burst transmitter according to claim 1. The tunable transmitter includes a tunable light source that outputs light having a wavelength determined by a wavelength switching signal, an external modulator that modulates light from the tunable light source with a data signal and outputs a continuous optical signal, With
The burst control unit includes a semiconductor optical amplifier (SOA), and amplifies the continuous optical signal when turned on by the burst control signal, and absorbs the continuous optical signal when turned off. The tunable burst transmitter according to claim 1. The wavelength tunable transmitter includes: a wavelength tunable light source that bursts light having a wavelength determined by a wavelength switching signal with a burst generation signal synchronized with the burst control signal and outputs burst light; and a burst from the wavelength tunable light source. An external modulator that modulates light with a data signal and outputs a burst optical signal,
The burst control unit includes: an optical amplifier that optically amplifies the burst optical signal; and a variable attenuation unit that transmits the burst optical signal when the burst control signal is turned on and blocks the burst optical signal when the burst control signal is turned off. The tunable burst transmitter according to claim 1. The tunable transmitter includes a tunable light source that outputs light having a wavelength determined by a wavelength switching signal, an external modulator that modulates light from the tunable light source with a data signal and outputs a continuous optical signal, With
The burst control unit includes an optical amplifier that optically amplifies the continuous optical signal, and a variable attenuating unit that transmits the continuous optical signal when the burst control signal is turned on and blocks the continuous optical signal when the burst control signal is turned off. The tunable burst transmitter according to claim 1.

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