JP2011044827A - Optical transmission apparatus and optical transmission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prolong life of a semiconductor laser itself and attain power saving by reducing the temperature of the semiconductor laser to lower operating ratio when the semiconductor laser is at high temperature and restarting transmission after emission efficiency is recovered. <P>SOLUTION: The temperature of the semiconductor laser LD is measured (S2), priority of data to be transmitted is determined, and stall amount of data corresponding to the priority is measured (S4, S6). When the measured temperature is higher than predetermined temperature T, and the backlog amount of the data of the predetermined measured priority is less than a predetermined amount M determined according to the priority, transmission of the data of the predetermined priority is stopped (S8), and when the backlog amount of the data of the priority is equal to or more than the predetermined amount M, the data of the priority is transmitted (S12). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical transmission apparatus and an optical transmission method using a semiconductor laser as a light source for transmission.

If an optical transmission device using a semiconductor laser as a light source is continuously operated for a long time, the temperature of the semiconductor laser rises due to the power consumption of the semiconductor laser and peripheral drive circuits, and the optical output is greatly reduced.
FIG. 9 is a graph showing the optical output of the semiconductor laser versus temperature. From this figure, if the temperature of the semiconductor laser rises, the threshold current of the semiconductor laser increases as the temperature rises. Therefore, driving to flow through the semiconductor laser to ensure the optical output (necessary value) necessary for communication It can be seen that it is necessary to greatly increase the current. This causes an increase in power consumption and a decrease in light emission efficiency indicating the ratio of light output to current.

  Further, the temperature rise and drive current increase of the semiconductor laser add chemical and physical stress to the semiconductor laser and degrade the characteristics. This shortens the life of the semiconductor laser itself and reduces the reliability of the device.

The increase in power consumption as described above not only goes against the recently demanded power saving, but also shortens the life of devices and devices and impairs reliability.
Accordingly, an object of the present invention is to extend the lifetime of the semiconductor laser itself by reducing the operating rate when the semiconductor laser is at a high temperature, lowering the temperature of the semiconductor laser, and restarting transmission after the light emission efficiency is restored. An object of the present invention is to provide an optical transmission device that can improve the reliability as a device and achieve power saving.

In order to achieve the above object, an optical transmission apparatus according to the present invention includes a temperature measurement unit that measures the temperature of a semiconductor laser, and determines the priority of data to be transmitted, and measures the amount of data stagnation corresponding to the priority. Stagnation amount measuring means to
A predetermined amount in which the temperature measured by the temperature measuring unit is higher than a predetermined temperature, and the stagnation amount of the data having the predetermined priority measured by the stagnation amount measuring unit is determined according to the priority. The current flowing to the semiconductor laser is suppressed or stopped to stop transmission of the data with the predetermined priority, and when the amount of stagnation of the data with the priority is equal to or greater than the predetermined amount, the priority Transmission control means for performing control to transmit the data of the degree.

  According to the present invention, when the temperature of the semiconductor laser is higher than a predetermined temperature, the data to be transmitted is selected according to the priority of the data. That is, when the stagnation amount of the data with the priority is smaller than the predetermined amount determined according to the priority, the transmission of the data with the priority is stopped. When the stagnation amount of the priority data is equal to or greater than the predetermined amount, the priority data is transmitted. By this control, it is possible to avoid an operation at a high temperature at which the light emission efficiency of the semiconductor laser is lowered. However, if transmission of high-priority data that requires real-time performance is stagnant, the service may be hindered. Therefore, such high-priority data is transmitted regardless of temperature.

  There are at least two priority levels, the stagnation amount measuring means measures the stagnation amount of the data with the highest priority and the stagnation amount of other low priority data, and the transmission control means measures the temperature. The temperature measured by the means is higher than the predetermined temperature, the stagnation amount of the data having the highest priority is less than the first predetermined amount M1 determined according to the priority, and the other priority is low. When the data stagnation amount is smaller than the second predetermined amount M2 determined according to the priority, the current flowing through the semiconductor laser may be suppressed or stopped. With this configuration, in order to maintain real-time performance (delay time) that does not impair data services with high priority, transmission control is performed based on the first predetermined amount M1, while other delay times are not a problem. Data can be controlled for transmission based on the second predetermined amount M2.

  Since the first predetermined amount M1 is a reference for data with high priority, it is preferable that the first predetermined amount M1 be smaller than the second predetermined amount M2 that is a criterion for determining the stagnation amount of data with low priority. Since the first predetermined amount M1 is an amount determined by, for example, the communication speed, and the second predetermined amount M2 is a reference for data whose delay time is not a significant problem, for example, the amount of data that can be held by the device (buffer memory amount) It is good also as the quantity decided by. In this way, for signals with different priorities (allowable delay times), fine settings can be made according to the amount of delay time or the amount of data buffer memory that can be held by the device, and high power efficiency can be achieved without affecting service. Transmission is possible.

  There are at least two predetermined temperatures (T1, T2; T2 <T1), and the transmission control means determines that the stagnation amount of the data of the predetermined priority measured by the stagnation amount measurement means corresponds to the priority. If the temperature measured by the temperature measuring means is higher than a predetermined temperature (T1) when the amount is less than a predetermined amount determined in this way, the current flowing through the semiconductor laser is suppressed or stopped, When the temperature measured by the temperature measuring unit becomes lower than a predetermined temperature (T2) from the state where the current flowing to the semiconductor laser is suppressed or stopped as described above, the priority data by the semiconductor laser is displayed. May be transmitted. As described above, by providing hysteresis at the temperature at which data transmission is stopped and the temperature at which data transmission is resumed, the transmission control operation of the present invention can be performed stably.

  Further, the optical transmission device of the present invention is an optical transmission device that transmits data by using an automatic power controlled semiconductor laser as a light source. The decrease in efficiency of the semiconductor laser is not an increase in temperature but an increase in the driving current of the semiconductor power controlled by the automatic power control. And the same control as that of the present invention described above can be performed. In other words, according to the second aspect of the present invention, the optical transmission device determines the priority of the data to be transmitted and the current measurement means for measuring the current flowing through the semiconductor laser, and the stagnation of the data corresponding to the priority A stagnation amount measuring means for measuring the amount, the current measured by the current measuring means is higher than a predetermined current value, and the stagnation amount of data of a predetermined priority measured by the stagnation amount measuring means is When the amount is smaller than a predetermined amount determined according to the priority, the current flowing to the semiconductor laser is suppressed or stopped, data transmission is stopped, and the stagnation amount of the data of the priority is equal to or larger than the predetermined amount. In some cases, transmission control means for performing control to transmit data of the priority is provided.

  According to the present invention, when the current flowing through the semiconductor laser is higher than a predetermined current value, the data to be transmitted is selected according to the priority of the data. That is, when the stagnation amount of the priority data is smaller than the predetermined amount, the transmission of the priority data is stopped. When the stagnation amount of the priority data is equal to or greater than a predetermined amount, the priority data is transmitted. By this control, it is possible to avoid an operation at a large current that reduces the light emission efficiency of the semiconductor laser. However, if transmission of high-priority data that requires real-time performance is stagnant, the service may be hindered. Therefore, such high-priority data is transmitted regardless of current.

  There are at least two levels of priority, and the measuring means measures the amount of stagnation of data with the highest priority and the amount of stagnation of other low priority data, and the transmission control means is a current measuring means. The measured current is higher than a predetermined current value, the stagnation amount of the highest priority data is less than the first predetermined amount M1 determined according to the priority, and other low priority data The current flowing through the semiconductor laser may be suppressed or stopped when the amount of stagnation is less than the second predetermined amount M2 determined according to the priority. With this configuration, in order to maintain real-time performance (delay time) that does not impair data services with high priority, transmission control is performed based on the first predetermined amount M1, while other delay times are not a problem. Data can be controlled for transmission based on the second predetermined amount M2.

  Since the first predetermined amount M1 is a reference for data with high priority, it is preferable that the first predetermined amount M1 be smaller than the second predetermined amount M2 that is a criterion for determining the stagnation amount of data with low priority. Since the first predetermined amount M1 is an amount determined by, for example, the communication speed, and the second predetermined amount M2 is a reference for data whose delay time is not a significant problem, for example, the amount of data that can be held by the device (buffer memory amount) It is good also as the quantity decided by.

  It is better to restart the stopped transmission after confirming that the current for driving the semiconductor laser has dropped sufficiently, but since it cannot be measured unless the optical output is actually sent through the semiconductor laser, this measurement is not possible. Such control is difficult. Therefore, it is better to measure the passage of time. That is, the timer operation is started after suppressing or stopping the current flowing to the semiconductor laser, and the transmission of the data of the priority by the semiconductor laser is resumed after a predetermined time elapses.

  If the optical transmitter of the present invention is a home-side device ONU in a passive optical network (PON), and the suppression or stop of the current flowing through the semiconductor laser is based on an instruction from the station-side device OLT of the passive optical network, The following effects are obtained. In the PON optical communication system, transmission from the home-side apparatus ONU to the station-side apparatus OLT is based on a burst transmission operation based on time division, and the optical transmission apparatus of the present invention is easily applied to this home-side apparatus ONU. be able to. Then, by transmitting information such as temperature status, semiconductor laser drive current, data stagnation amount from the home device ONU to the station device OLT, by instructing the home device ONU on the station device OLT side, The current flowing through the semiconductor laser of the home device ONU can be controlled. In this case, the station side device OLT can be centrally managed and controlled, and the uplink transmission time can be assigned to another home side device ONU instead of the home side device ONU that stopped transmission, and communication is performed as a whole. Efficiency can be improved.

  An optical transmission method according to the present invention is an optical transmission method according to the substantially same invention as the invention according to the above-described optical transmission device.

As described above, according to the present invention, transmission is stopped in a high temperature state where the light emission efficiency is lowered by measuring the temperature of the semiconductor laser, and transmission is started after the semiconductor laser temperature is lowered and the light emission efficiency is recovered. As a result, the power efficiency is improved, and the operating temperature and the drive current are reduced, so that the failure rate of components such as a semiconductor laser is reduced.
In addition, to stop transmission in a high temperature state where the light emission efficiency decreases by measuring the driving current of the semiconductor laser controlled automatically, to start transmission after the semiconductor laser temperature is reduced and the light emission efficiency is recovered, As the power efficiency is improved, the operating temperature and the driving current are reduced, so that the failure rate of components such as a semiconductor laser is reduced.

It is the schematic which shows the structural example of the PON optical communication system which connected between the station side apparatus OLT and several home side apparatus ONU with the optical fiber via the optical coupler. FIG. 3 is a block diagram showing an optical transmission device that is provided in a home-side device ONU of a PON optical communication system and transmits data stored in a data buffer memory using a semiconductor laser LD as a light source. It is a partially cutaway perspective view showing the arrangement of the semiconductor laser LD in the module. It is a figure which shows the outline of the drive substrate of semiconductor laser LD. It is a flowchart for demonstrating the procedure of performing transmission / transmission stop of data according to the temperature of semiconductor laser LD, and the amount of stagnation of the data to transmit. It is a graph which shows the historical relationship between the temperature of semiconductor laser LD, and the transmission / transmission stop state of data. It is a flowchart for demonstrating the procedure which performs transmission / transmission stop of data according to the electric current which flows into the semiconductor laser LD by which automatic power control was carried out, and the amount of stagnation of the data to transmit. It is a flowchart for demonstrating the procedure which performs transmission / transmission stop of the home side apparatus ONU of a PON optical communication system by the instruction | indication from the station side apparatus OLT. It is a flowchart (continuation of FIG. 8A) for demonstrating the procedure which performs transmission / transmission stop of the home side apparatus ONU of a PON optical communication system by the instruction | indication from the station side apparatus OLT. It is a graph which shows the relationship between the optical output of semiconductor laser LD, and temperature.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram illustrating a configuration example of a PON optical communication system.
In the PON optical communication system, a station side device OLT provided in a station building and a home side device ONU provided in a plurality of subscribers are connected via an optical fiber SMF and an optical coupler OC.
The home-side apparatus ONU includes a network interface for connecting a terminal for enjoying an optical network service such as a personal computer installed in the subscriber's home.

The optical coupler OC is composed of a star coupler that passively branches and multiplexes a signal from an input signal without requiring an external power supply.
The optical fibers connected to the station-side device OLT, the optical coupler OC, the optical coupler OC, and the home-side device ONU are single mode fibers each composed of one optical fiber SMF. That is, one station side apparatus OLT is connected to the first optical coupler OC through one trunk optical fiber SMF. The first optical coupler OC is connected to M second optical couplers OC (M is a number of 1 in this example) by an optical fiber SMF, if necessary. The first and second optical couplers OC are connected to a plurality of home-side devices ONU via branch line optical fibers SMF. Therefore, a signal transmitted / received by one station-side apparatus OLT is distributed to a plurality of home-side apparatuses ONU by a two-stage optical coupler OC. Note that the numbers of the optical couplers OC and the home-side devices ONU are merely examples.

The optical communication system according to the embodiment of the present invention incorporates the technology of Ethernet (Ethernet is a registered trademark) into the PON optical communication system, and realizes optical fiber access section communication at a baseband speed of Gbps. GE-PON (Gigabit Ethernet-Passive Optical Network) system is adopted.
According to the GE-PON system, the communication between the station side device OLT and the home side device ONU is performed in units of variable length frames.

  First, a downlink frame that enters each station-side apparatus OLT in a broadcast form from a higher-level network is subjected to predetermined processing in the station-side apparatus OLT, and a logical link (referred to as an MPCP link) to be relayed is specified. Then, it is transmitted to the optical fiber SMF as an optical signal through the station side device OLT. The optical signal transmitted to the optical fiber SMF is branched by the optical coupler OC and transmitted to the home device ONU connected to the optical coupler OC, but only the home device ONU constituting the MPCP link transmits a predetermined downlink frame. Capture and relay frame to home network interface.

  On the other hand, the upstream optical signal includes an upstream frame from each home-side apparatus ONU. The upstream optical signal needs to be transmitted so that the optical signals from the respective home devices ONU do not compete with each other in time. For this purpose, the station-side apparatus OLT allocates a window (hereinafter simply referred to as “window”) during which an upstream optical signal may be transmitted to each home-side apparatus ONU and notifies it as an uplink bandwidth allocation control frame. The home-side apparatus ONU to which the window is assigned transmits an upstream optical signal during the assigned window period. This upstream optical signal is referred to as a “burst optical signal”. The burst optical signal is a finite-time optical signal sequence which is transmitted from each home-side apparatus ONU and whose light emission state is changed by the baseband signal.

Therefore, the competition of the upstream optical signal between each home-side apparatus ONU is avoided. Each home-side apparatus ONU, when given a certain window, may transmit frames continuously as long as it fits in that window. The station apparatus OLT can receive a burst optical signal including a series of frame signals from each home apparatus ONU.
FIG. 2 is a schematic circuit diagram of the optical transmitter 10 using the semiconductor laser LD in the present embodiment. The optical transmission device 10 is provided in a home device ONU.

  The optical transmitter 10 includes an optical transmitter 1 that optically transmits data using a semiconductor laser LD as a light source, a data buffer 2 that stores transmission data, and a stagnation amount of transmission data corresponding to each priority (not transmitted to the data buffer 2) And the amount of stagnation of the transmission data with the predetermined priority that is measured is determined according to the priority. A controller 3 that performs control to suppress or stop the current flowing through the semiconductor laser LD when the amount is smaller than a predetermined amount, and a MAC-IC transmission signal generation unit 4 that generates a transmission signal based on transmission data ing.

The optical transmitter 1 includes a modulation current source Am, a bias current source Ab, an APC / ER control circuit 5, an optical link substrate 9 on which a temperature sensor 7 is mounted, a laser on which a semiconductor laser LD and a monitoring photodiode PD are mounted. A module 6 is included.
In the optical link substrate 9, a bias current source Ab that supplies a bias current Ib and a modulation current source Am that supplies a modulation current Im are connected to a semiconductor laser LD that transmits an optical signal. The signal a for controlling the modulation current Im and the signal b for controlling the bias current Ib are created by the APC / ER control circuit 5. The output light of the semiconductor laser LD is emitted from the irradiation end, is input to an optical fiber (not shown), propagates through the optical fiber, and is received by the partner station.

The optical link substrate 9 further includes a temperature sensor 7 for measuring the temperature of the semiconductor laser LD or the vicinity thereof. The temperature sensor 7 may be, for example, a thermocouple or thermistor that is installed in the vicinity of the laser module 6 described below and measures its temperature.
FIG. 3 is a partially cutaway perspective view showing the internal structure of the laser module 6.

  The laser module 6 includes a heat sink 14 on a bottom plate 16 with a cap 17, and a semiconductor laser LD is mounted thereon. The cap 17 accommodates a photodiode PD for monitoring the light emission of the semiconductor laser LD. The photodiode PD is installed at a position where the output light of the semiconductor laser LD can be detected (such as an irradiation end on the opposite side). For example, the semiconductor laser LD is of a type that emits light from two output windows so that an optical signal to be irradiated for communication can be monitored by the photodiode PD. Such a structure can be realized by making the front and rear edge of the semiconductor laser LD translucent.

A plurality of electrode terminals 15 are introduced into the bottom plate 16. A non-reflective coating glass plate 18 is attached to the opening of the cap 17, and the output light of the semiconductor laser LD is applied to the end face of the external optical fiber through the glass plate 18.
The light emission of the semiconductor laser LD is detected by the photodiode PD, and this detection signal is supplied to the optical link substrate 9 for drive control of the laser diode.

FIG. 4 is a diagram showing a state where the laser module 6 is connected to the optical link substrate 9. Of the electrode terminals 15 of the laser module 6, an electrode terminal 15a connected to the semiconductor laser LD and an electrode terminal 15b connected to the photodiode PD are shown.
Through the wiring on the optical link substrate 9, the output terminals of the modulation current source Am and the bias current source Ab are connected to the electrode terminal 15a, and the electrode terminal 15b connected to the photodiode PD is connected to the input terminal of the APC / ER control circuit 5. The

The detected photocurrent of the photodiode PD is converted into a voltage signal and input to the APC / ER control circuit 5 as shown in FIG. For example, the peak value of the detected photocurrent is detected by the signal processing function of the APC / ER control circuit 5. Based on this peak value, the amplitude of the modulation current Im is controlled so that the effective transmission light output of the semiconductor laser LD becomes a target value.
On the other hand, a temperature sensor 7 is connected to the APC / ER control circuit 5. A table for setting an optimum bias current based on the temperature reading value of the temperature sensor 7 is prepared in the ROM of the APC / ER control circuit 5. In this table, a bias current value is defined so as to obtain a desired extinction ratio according to temperature. This bias current value is set in the bias current source Ib.

With the above automatic power control, a transmission effective light output as a target value can be obtained and a desired extinction ratio can be obtained. Can be made constant.
In addition, a high-speed switching element SW for creating an intermittent burst transmission signal is provided in series with the modulation current source Am. The on / off command signal of the switching element SW is generated by the MAC-IC transmission signal generation circuit 4. The MAC-IC transmission signal generation circuit 4 is connected to a data buffer 2 that temporarily stores transmission data for creating a burst transmission signal to be transmitted.

In this optical transmitter 10, as shown in FIG. 2, a normally closed contact B1 for interrupting the modulation current source Am is provided in series with the modulation current source Am. Further, a normally closed contact B2 for cutting off the bias current source Ab is provided in series with the bias current source Ab. These contacts B1 and B2 are opened and closed based on a command from the controller 3.
The controller 3 can obtain the amount of stagnation of transmission data stored in the data buffer 2 and the priority information of the transmission data from the data buffer.

Table 1 lists examples of priorities corresponding to the traffic type, usage, and required quality of transmission data.
Among the transmission data, there is data with high priority (short allowable delay time) that requires real-time characteristics, such as telephone audio signals and videophone video signals. For these, if the amount of stagnation is large, it will hinder the provision of services. Therefore, the first predetermined amount M1 is set, and if it is confirmed that the amount of stagnation is equal to or greater than the first predetermined amount M1, transmission is performed. Only when the amount is less than the first predetermined amount M1, the current flowing through the semiconductor laser LD is set to zero (OFF).

  In addition, there is data with low priority (long allowable delay time) that requires real-time performance. For example, there is data that is used for mission-critical operations, bandwidth-guaranteed data such as important data, or data that is not bandwidth-guaranteed for web access, file transfer, and backup processing. In these data, a second predetermined amount M2 larger than the first predetermined amount M1 is set, and if it is confirmed that the amount of stagnation is equal to or larger than the second predetermined amount M2, transmission is performed. Only when the amount is less than the second predetermined amount M2, the current flowing through the semiconductor laser LD is set to zero (OFF).

When the allowable amount of the data holding data buffer 2 is exceeded, transmission is performed for a predetermined time regardless of the measured temperature.
Hereinafter, the controller has a temperature measured by the temperature sensor 7 higher than a predetermined temperature, and the amount of stagnation of the highest priority data is less than a first predetermined amount M1 determined according to the priority, And when the amount of stagnation of the other low-priority data is smaller than a second predetermined amount M2 determined according to the priority, the flow of processing for suppressing or stopping the current flowing to the semiconductor laser is explain.

As described above, it is assumed that the controller obtains information on the priority of data to be transmitted and information on the amount of stagnation of data with the priority from the data buffer.
The controller uses the priority information and the stagnation amount information so that the temperature measured by the temperature sensor 7 is higher than the predetermined temperature and the stagnation amount of the data with the predetermined priority is less than the predetermined amount. Sometimes, the current flowing to the semiconductor laser LD is suppressed or stopped, and when the stagnation amount of the priority data is equal to or greater than a predetermined amount, control to transmit the priority data is performed. This procedure will be described with reference to a flowchart (FIG. 5) and a graph (FIG. 6).

  First, a standby flag indicating a data transmission state or a stop state is set to 0 (transmission state) (step S1). Next, a measured value of the temperature around the semiconductor laser LD by the temperature sensor 7 is acquired (step S2), and it is determined whether or not the temperature is higher than a predetermined temperature T1 (step S3). This “predetermined temperature T1” is set to a temperature at which the emission efficiency indicating the ratio of the optical output with respect to the current decreases remarkably when the semiconductor laser LD continues to oscillate further.

  If the temperature is higher than the temperature T1, the stagnation amount of a signal having a high priority (short allowable delay time) is measured (step S4). If the stagnation amount of the high priority signal is equal to or greater than the predetermined amount M1 (step S5), the process proceeds to step S12. The predetermined amount M1 is a stagnation determination reference amount for transmitting data regardless of the measured temperature when a signal having a high priority is stagnating to the extent that the service is hindered. For example, if the design policy is that no stagnation of high priority signals is allowed, the predetermined amount M1 may be set as the minimum unit (for example, 1 byte) of transmission data.

  If the stagnation amount of the signal with high priority is less than the predetermined amount M1, the process proceeds to step S6, and the stagnation amount of the signal with low priority (long allowable delay time) is measured (step S6). If the stagnation amount of the low priority signal is equal to or greater than the predetermined amount M2 (step S7), the process proceeds to step S12. The predetermined amount M2 may be an allowable amount of the data holding data buffer 2 included in the device. When the predetermined amount M2 is exceeded, transmission is performed for a predetermined time regardless of the measured temperature. The relationship between the predetermined amount M1 and the predetermined amount M2 is M1 <M2.

  If the stagnation amount of the low-priority signal is less than the predetermined amount M2, the controller issues a command signal to open the contacts B1 and B2 for cutting off the modulation current source Am and the bias current source Ab. Thereby, the bias current / modulation current of the semiconductor laser LD is turned off, and the optical transmission from the semiconductor laser LD is stopped (step S8). After the optical transmission is stopped, the standby flag indicating the transmission state or the stop state is set to 1 (stop state) (step S9), and the process returns to step S2.

It is also conceivable to set a small current for standby instead of completely turning off the bias current / modulation current of the semiconductor laser LD. In this way, the term “suppresses or stops” the current flowing through the semiconductor laser, including not only the case where the current is completely stopped, but also the flow of a small current is used.
Next, if the temperature around the semiconductor laser LD measured by the temperature sensor 7 is lower than the temperature T1 in step S3, the process proceeds to step S10, and it is determined whether or not the temperature is lower than the predetermined temperature T2. Here, T2 <T1.

  If it is higher than the temperature T2, the temperature around the semiconductor laser LD is between T2 and T1. In this case, the behavior is changed according to the value of the standby flag. When the standby flag is 1 (stopped state), the process proceeds to step S4 and is handled in the same manner as when the temperature is higher than the temperature T1. That is, as can be seen from FIG. 6, in the stop state, the transmission is not resumed unless the temperature falls to T2. When the standby flag is 0 (transmission state), the process proceeds to step S12 and is handled in the same manner as when the temperature is lower than T2. That is, as shown in FIG. 6, in the transmission state, if the temperature does not rise to T1, the procedure is such that it does not stop. In this way, since the temperature hysteresis operation can be realized, it is possible to prevent the adverse effect of frequent switching between transmission and stop.

If the temperature around the semiconductor laser LD is lower than the temperature T2 in step S10, the process proceeds to step S12.
In step S12, the controller issues a command signal to close the contacts B1 and B2 in order to conduct the modulation current source Am and the bias current source Ab. Thereby, the suppression or stop of the current of the semiconductor laser LD is released, and the optical transmission from the semiconductor laser LD is resumed. In this case, the order of transmission is such that a signal with a high priority is transmitted first, and a signal with a low priority is transmitted later. The upper limit of the transmission amount is a fixed amount M3. This fixed amount M3 is data corresponding to the maximum value of the data amount transmitted at one time. For example, the fixed amount M3 may be set to a value equal to the allowable amount of the data buffer 2.

After the optical transmission is resumed, a standby flag indicating whether the transmission is in the transmission state or the stop state is set to 0 (transmission state) (step S13), and the process returns to step S2.
As described above, the temperature of the semiconductor laser LD or its surroundings is measured. (1) When the temperature is equal to or lower than the temperature T2, the semiconductor laser LD is driven to send all data. (2) When the temperature is equal to or higher than T1, the current flowing through the semiconductor laser LD is suppressed or stopped, and the temperature is lowered to recover the light emission efficiency. However, if high-priority data is stagnating for a predetermined amount M1 or more, that data is sent, and if low-priority data is stagnating for a predetermined amount M2 or more, that data is sent. If completed, the current flowing through the semiconductor laser LD is suppressed or stopped. (3) When the temperature T2 <T <T1, the temperature hysteresis operation can be realized by performing either the operation (1) or (2) according to the value of the standby flag.

Next, another embodiment of the present invention will be described. In this embodiment, instead of measuring the temperature of the semiconductor laser LD or the vicinity thereof, the bias current, the modulation current, or the total current of the APC-controlled semiconductor laser LD is measured, and the semiconductor is based on the measured value. This is to indirectly estimate the light emission efficiency of the laser LD.
In this process, the controller uses the priority information and the stagnation amount information of the transmission data stored in the data buffer to measure the bias current, the modulation current, or the total current (hereinafter referred to as “drive current”). ) Is higher than a predetermined current value and the stagnation amount of data of a predetermined priority is smaller than the predetermined amount, the drive current flowing to the semiconductor laser LD is suppressed or stopped, and the stagnation of the data of the priority When the amount is greater than or equal to the predetermined amount, control is performed to transmit data of the priority. This procedure will be described with reference to a flowchart (FIG. 7).

In this procedure, unlike the temperature, the drive current cannot be measured unless the semiconductor laser emits light. Therefore, transmission is resumed by determining the time sufficient for the semiconductor laser to sufficiently cool and recover the light emission efficiency.
Referring to the flowchart (FIG. 7), first, a timer for measuring the time required to recover the light emission efficiency by reducing or stopping the drive current flowing through the semiconductor laser LD and resetting the light emission efficiency is reset (step). T1). The reason for using the timer is that once the semiconductor laser LD is turned off, the drive current cannot be measured until the semiconductor laser LD is turned on again. This is to start energization of the semiconductor laser LD by determining the time when the LD temperature is lowered and the light emission efficiency is expected to be recovered.

  Next, the drive current flowing through the semiconductor laser LD is measured based on information from the APC / ER control circuit 5 (step T2), and it is determined whether or not the drive current is higher than a predetermined current value (step T3). If the current value is higher than the predetermined current value, the timer operation is started (step T4), and the stagnation amount of the high priority signal (short allowable delay time) is measured until the timer counts up the predetermined time (step T5). (Step T6). If the stagnation amount of the high priority signal is equal to or greater than the predetermined amount M1 (step T7), the process proceeds to step T11. This predetermined amount M1 is a stagnation determination reference amount for performing transmission regardless of the measured drive current when a signal with a high priority is stagnant to the point of impeding service. For example, if the design policy is that no stagnation of high priority signals is allowed, the predetermined amount M1 may be set to the minimum unit of data (for example, 1 byte).

  If the stagnation amount of the signal with high priority is less than the predetermined amount M1, the stagnation amount of the signal with low priority (long allowable delay time) is measured (step T8). If the stagnation amount of the low-priority signal is equal to or greater than the predetermined amount M2 (step T9), the process proceeds to step T11. The predetermined amount M2 may be an allowable amount of the data buffer 2. When the predetermined amount M2 is exceeded, transmission is performed by the predetermined amount M3 regardless of the measured current value.

  If the stagnation amount of the low priority signal is less than the predetermined amount M2, the controller issues a command signal to open the contacts B1 and B2 for shutting off the modulation current source Am and the bias current source Ab (step T10) Thereby, the bias current / modulation current of the semiconductor laser LD is turned off, and the optical transmission from the semiconductor laser LD is stopped. After the optical transmission is stopped, the process returns to step T5.

In step T5, it is determined whether the timer has counted up a predetermined time. If the timer counts up the predetermined time, the process proceeds to step T11.
In step T11, the controller estimates that the light emission efficiency of the semiconductor laser LD has recovered since a predetermined time has elapsed, and issues a command signal to close the contacts B1 and B2 in order to connect the modulation current source Am and the bias current source Ab. put out. Thereby, driving of the semiconductor laser LD and optical transmission are resumed. In this case, the transmission amount is a fixed amount M3. This fixed amount M3 is data corresponding to the upper limit value of the amount of optical signal transmitted at one time. The certain amount M3 is an allowable amount of the data buffer 2, for example.

Then, after resuming optical transmission, the timer is reset and the process returns to step T2.
As described above, the drive current of the semiconductor laser LD is measured. (1) When the current is equal to or less than a predetermined current value, the current is sent to the semiconductor laser LD to send data. (2) When the current value is equal to or greater than the predetermined current value, the current flowing through the semiconductor laser LD is suppressed or stopped, and the temperature is lowered and the light emission efficiency is restored to wait for a predetermined time by the timer. However, if high-priority data is stagnating for a predetermined amount M1 or more, the data can be sent. If low-priority data is stagnating for a predetermined amount M2 or more, the data can be sent.

  Next, still another embodiment of the present invention will be described. In this embodiment, in a PON (Passive Optical Network) optical communication system that performs optical communication via an optical branching unit between a station-side device OLT and a plurality of home-side devices ONU, the station-side device OLT is connected to each home-side device. The ONU inquires about the amount of stagnation data, and the home side device ONU reports whether the stagnation amount is a predetermined amount to the station side device OLT. If the stagnation amount is a predetermined amount, the station side device OLT A transmission slot is allocated to the home-side apparatus ONU, and if the amount of stagnation is not a predetermined amount, a notification that no transmission slot is allocated to the home-side apparatus ONU is notified. Upon receiving this slot assignment or notification, the home apparatus ONU transmits the stagnant data, or suppresses or stops the current of the semiconductor laser LD to stop transmission.

  FIG. 8A and FIG. 8B are flowcharts showing the cooperation between the station side device OLT and the home side device ONU in the optical communication system. In the flowchart, the operation of the station-side device OLT and the operation of the home-side device ONU are shown as separate flows, but when there is cooperation, the cooperation is indicated by a broken line. If the content of each block is the same as that shown in FIG. 5, the same symbol “S number” as that shown in FIG.

First, the station-side apparatus OLT sets a minimum compensation band for each home-side apparatus ONU before starting communication (step U1). The minimum compensation band is a band that is always set between the station-side apparatus OLT and the home-side apparatus ONU, and transmits minimum information (for example, a communication start request command) from the home-side apparatus ONU. It is a band that can be.
The station side device OLT inquires each home side device ONU about the amount of stagnation data (step U2). In response to this inquiry, the home-side apparatus ONU measures the temperature around the semiconductor laser LD by the temperature sensor 7 (step S2), as described with reference to the flowchart (FIG. 5), and starts from the predetermined temperature T1. If it is high, the stagnation amount of the high priority signal is measured (step S4), and if the stagnation amount of the high priority signal is equal to or greater than the predetermined amount M1 (step S5), the station side device OLT has the stagnation amount, priority, The bandwidth allocation amount and the temperature information around the semiconductor laser LD are reported (step S12a). The reason for reporting the stagnation amount and the like in this way is to acquire slot bandwidth allocation for transmitting the stagnation data from the station side device OLT.

  If the stagnation amount of the high-priority signal is less than the predetermined amount M1, the process proceeds to step S6, where the stagnation amount of the low-priority signal is measured. If it is equal to or greater than the predetermined amount M2 (step S7), the stagnation amount, priority, requested bandwidth allocation amount, and temperature information around the semiconductor laser LD are reported to the station side device OLT (step S12a). The reason why the requested bandwidth is reported in this way is to acquire the slot bandwidth allocation for transmitting the stagnant data from the station side device OLT.

If the stagnation amount of the low priority signal is less than the predetermined amount M2, the station side device OLT reports that there is no stagnation amount (step S8a).
After receiving these reports from the home device ONU, the station device OLT determines whether or not transmission of data from the home device ONU to the station device OLT should be permitted (step U3). Further, when the transmission of data from the home device ONU to the station device OLT is permitted, the bandwidth allocation amount requested from the home device ONU is determined (step U5).

If the bandwidth allocation amount is larger than the minimum compensation bandwidth, the surplus bandwidth excluding the minimum compensation bandwidth for each home-side device ONU is used and corresponds to the minimum compensation bandwidth according to the ratio of the required bandwidth of each home-side device ONU A slot band to be assigned is assigned (step U6).
If the bandwidth allocation amount is smaller than the minimum compensation bandwidth, it is sufficient to use the minimum compensation bandwidth. Therefore, no additional slot bandwidth is assigned to each home-side apparatus ONU (step U7). The processing of the rear station side device OLT returns to Step U2.

When the slot bandwidth is assigned to the home device ONU, the home device ONU is notified that the slot bandwidth is assigned or the slot bandwidth is not assigned (step U8).
When receiving the notification to which the slot band is assigned (step S14), the home apparatus ONU transmits the data that is stagnant according to the assigned slot if the slot band is assigned. When the notification not assigning the slot band is received, the current of the semiconductor laser LD is cut off by cutting off the modulation current source Am and the bias current source Ab (step S15).

  In this way, in the PON optical communication system, the home apparatus ONU reports the stagnation amount, priority, requested bandwidth allocation amount, and temperature information around the semiconductor laser LD to the station apparatus OLT, and there is no stagnation. Sometimes the station side device OLT notifies the home side device ONU that the slot band is not allocated, and upon receiving this notification, the home side device ONU suppresses or stops the current flowing through the semiconductor laser LD. Therefore, the temperature of the semiconductor laser LD can be lowered to recover the light emission efficiency. Further, since the station side device OLT can know information such as the amount of stagnation of transmission data of each home side device ONU, the station side device OLT can efficiently allocate slot bandwidth to the home side device ONU in which transmission data is stagnant. Can do.

  Although the embodiment of the present invention has been described above, it should be considered that the embodiment of the present invention is illustrative and not restrictive in all respects. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Optical transmission part 2 Data buffer 3 Controller 4 MAC-IC transmission signal generation part 5 APC / ER control circuit 6 Laser module 7 Temperature sensor 9 Optical link board 10 Optical transmission apparatus

Claims (11)

In an optical transmission device that transmits data using a semiconductor laser as a light source,
A temperature measuring means for measuring the temperature of the semiconductor laser, and a stagnation amount measuring means for determining a priority of data to be transmitted and measuring a stagnation amount of data corresponding to the priority,
A predetermined amount in which the temperature measured by the temperature measuring unit is higher than a predetermined temperature, and the stagnation amount of the data having the predetermined priority measured by the stagnation amount measuring unit is determined according to the priority. The current flowing to the semiconductor laser is suppressed or stopped to stop transmission of the data with the predetermined priority, and when the amount of stagnation of the data with the priority is equal to or greater than the predetermined amount, the priority An optical transmission apparatus comprising: a transmission control unit that performs control to transmit data of a predetermined degree. The priority has at least two stages,
The stagnation amount measuring means measures the stagnation amount of data having the highest priority and the stagnation amount of other low priority data,
The transmission control means includes a first predetermined amount (a predetermined amount (the amount of stagnation of the highest priority data) determined according to the priority, wherein the temperature measured by the temperature measurement means is higher than the predetermined temperature. M1) and the amount of stagnation of the other low-priority data is less than a second predetermined amount (M2) determined according to the priority, and the current flowing to the semiconductor laser is suppressed. The optical transmission device according to claim 1, wherein the optical transmission device is stopped.   The first predetermined amount (M1), which is a criterion for determining the stagnation amount of the data with the highest priority, is smaller than the second predetermined amount (M2), which is a criterion for determining the stagnation amount of the low priority data. The optical transmission device according to claim 2, which is a value. There are at least two predetermined temperatures (T1, T2; T2 <T1),
The transmission control means is measured by the temperature measurement means when the stagnation amount of the data of the predetermined priority measured by the stagnation amount measurement means is smaller than a predetermined amount determined according to the priority. If the temperature is higher than a predetermined temperature (T1), the current flowing to the semiconductor laser is suppressed or stopped, and the temperature measurement is performed from the state where the current flowing to the semiconductor laser is suppressed or stopped as described above. The light according to any one of claims 1 to 3, wherein when the temperature measured by the means becomes lower than a predetermined temperature (T2), the data of the priority is transmitted by the semiconductor laser. Transmitter device. In an optical transmitter that transmits data using a semiconductor laser with automatic power control as a light source,
Current measuring means for measuring a current flowing through the semiconductor laser, and a stagnation amount measuring means for determining a priority of data to be transmitted and measuring a stagnation amount of data corresponding to the priority,
The current measured by the current measuring means is higher than a predetermined current value, and the stagnation amount of the data with the predetermined priority measured by the stagnation amount measuring means is determined according to the priority. When less than the fixed amount, the current flowing to the semiconductor laser is suppressed or stopped, the transmission of the data of the predetermined priority is stopped, and when the stagnation amount of the data of the priority is the predetermined amount or more, An optical transmission apparatus comprising: a transmission control unit that performs control to transmit priority data. The priority has at least two stages,
The stagnation amount measuring means measures the stagnation amount of data having the highest priority and the stagnation amount of other low priority data,
The transmission control means is a first predetermined amount in which the current measured by the current measuring means is higher than a predetermined current value and the stagnation amount of the highest priority data is determined according to the priority. If the amount of stagnation of the other low-priority data that is smaller than (M1) is smaller than the second predetermined amount (M2) determined according to the priority, the current that flows to the semiconductor laser is The optical transmitter according to claim 5, wherein the optical transmitter is suppressed or stopped.   The first predetermined amount (M1), which is a criterion for determining the stagnation amount of the data with the highest priority, is smaller than the second predetermined amount (M2), which is a criterion for determining the stagnation amount of the low priority data. The optical transmission device according to claim 6, which is a value.   The transmission control unit is configured to supply a current to be supplied to the semiconductor laser when the stagnation amount of data having a predetermined priority measured by the stagnation amount measurement unit is smaller than a predetermined amount determined according to the priority. The optical transmission device according to any one of claims 5 to 7, wherein a timer operation is started after being suppressed or stopped, and data of the priority is transmitted by the semiconductor laser after a predetermined time has elapsed.   A home in a passive optical network (PON) optical communication system in which the optical transmitter performs optical communication via an optical branching unit between a station side device (OLT) and a plurality of home side devices (ONU). 9. The apparatus according to claim 1, wherein the current flowing through the semiconductor laser is suppressed or stopped by an instruction from the local apparatus (OLT) of the passive optical network (PON). The optical transmitter according to any one of the above. An optical transmission method for transmitting data using a semiconductor laser as a light source,
Measure the temperature of the semiconductor laser, determine the priority of data to be transmitted, measure the amount of stagnation of data corresponding to the priority,
The semiconductor laser when the measured temperature is higher than a predetermined temperature and the stagnation amount of the measured data of the predetermined priority is smaller than a predetermined amount determined according to the priority The transmission of the data of the predetermined priority is stopped, the transmission of the data of the predetermined priority is stopped, and when the stagnation amount of the data of the priority is equal to or greater than the predetermined amount, the control of transmitting the data of the priority is performed. The optical transmission method characterized by the above-mentioned. An optical transmission method for transmitting data using a semiconductor laser with automatic power control as a light source,
Measure the current flowing through the semiconductor laser, determine the priority of data to be transmitted, measure the amount of stagnation of data corresponding to the priority,
The semiconductor when the measured current is higher than a predetermined current value and the stagnation amount of the measured data of the predetermined priority is smaller than a predetermined amount determined according to the priority The control of transmitting the data of the priority is suppressed when the current flowing to the laser is suppressed or stopped, the transmission of the data of the predetermined priority is stopped, and the stagnation amount of the data of the priority is equal to or greater than the predetermined amount. An optical transmission method characterized in that:

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