CN201066762Y

CN201066762Y - Laser driving circuit

Info

Publication number: CN201066762Y
Application number: CNU2007201209202U
Authority: CN
Inventors: 夏京盛; 黄伟毅; 姚海军
Original assignee: Shenzhen Neo Photonic Technology Co Ltd
Current assignee: Shenzhen Apat Optoelectronics Components Co., Ltd.
Priority date: 2007-06-19
Filing date: 2007-06-19
Publication date: 2008-05-28
Anticipated expiration: 2017-06-19

Abstract

The utility model provides a driving circuit of a laser, comprising a laser component TOSA which is assembled by a thermoelectric cooler TEC and a laser diode LD, a LD driver and a TEC driver. An anode of the laser diode LD is connected with a slowly starting circuit which comprises a MOSFET tube, a first resistance R1, a second resistance R2 and a capacitance C1. The anode of the laser diode LD is connected with a drain electrode of the MOSFET tube. One end of the first resistance R1 is connected with a turn-off foot Txdis of the LD driver, and the other end is connected with a grid electrode of the MOSFET tube. The second resistance R2 and the capacitance C1 are in parallel connection to form an electricity-charging-and-discharging loop, one end of which is grounded, and the other end of the loop is connected with the grid electrode of the MOSFET tube. A source electrode of the MOSFET tube is connected with an electrical source Vcc. The utility model can increase a driving current slowly, when the laser diode LD is started, can reduce the temperature increasing velocity of the laser and reduces the wavelength float of the laser.

Description

Drive circuit for laser

Technical field

The utility model relates to the drive circuit for laser that is used for a kind of dense wave division multipurpose (being called for short DWDM) transfer of data, relates in particular to a kind of drive circuit for laser of the miniaturization hot plug SFP integrated module of optical transceiver.

Background technology

In dwdm system, in same optical fiber, need to transmit wavelength optical signals, the interval of each road light signal increases along with the dense degree of multiplex channel and constantly reduces, and the system of 100 wavelength comes into operation so far.Along with development of technology, more the system of multi-wavelength will emerge successively, and interchannel interval will be more and more littler.Because the channel spacing of different wave length is very little, for the light that guarantees mutual channel does not clash, the laser wavelength of module transmitting terminal just must keep advantages of higher stability.In the dwdm system as the 100GHz that operating at present, different channel spacings have only 0.8nm, system manufacturer require laser open and its centre wavelength of shutdown moment in λ c-0.2nm to λ c+0.2nm scope.Be the stable laser wavelength, now generally adopt drive circuit for laser as shown in Figure 1, comprise a laser assembly TOSA10, this assembly is integrated by a laser diode LD 11 and a thermoelectric refrigerating unit TEC12, the anode of laser diode LD connects power Vcc, negative electrode connects LD driver 20, the Transistor-Transistor Logic level of shutoff pin Txdis by LD driver 20 is controlled the conducting of the bias current (Ibias) of laser diode LD 11 and modulated current (Imod) and is ended, thermoelectric refrigerating unit TEC12 connects TEC drive circuit 30, one thermistor is embedded in the TOSA10, variation by this thermistor resistance feeds back to TEC drive circuit 30, and change size and Orientation (the forward refrigeration of TEC drive current according to feedback quantity, oppositely heat), be used to reach the purpose of stabilized lasers diode LD11 temperature.This drive circuit for laser can be controlled the wavelength output of laser assembly TOSA10 under stable state well, but in the moment that laser is opened, the drive current that increases can produce the bigger drift of output wavelength suddenly.As shown in Figure 2 laser is opened sequential chart, when the shutoff pin Txdis of LD driver 20 level during from the high level saltus step to low level, at t ₁Sudden change has taken place in time inner laser device luminous power, its used time is less than 1ms, a large amount of drive currents flows through laser diode LD 11 in the so very brief time, the temperature of laser tube core is sharply raise, in this moment, because can there be hysteresis in LD temperature transfer to thermistor, TEC drive circuit 30 can not be made the size and Orientation that reflection fast changes the TEC drive current immediately, can not in time regulate the temperature of laser diode LD 11, it is a lot of that laser moment working temperature exceeds normal working temperature, thereby cause the moment wavelength to exceed about stable state 1nm, certainly will cause interference, make system's cisco unity malfunction adjacent channel.

Summary of the invention

For overcoming above shortcoming, the utility model provides a kind of can reduce the drive circuit for laser that laser is opened the moment wave length shift.

For reaching above goal of the invention, the utility model provides a kind of drive circuit for laser, comprise a laser assembly TOSA, this assembly is integrated by a thermoelectric refrigerating unit TEC and a laser diode LD, one LD driver, one TEC driver, the anode of described laser diode LD connects a slow start circuit, this slow start circuit comprises: MOSFET pipe, first resistance R 1, second resistance R 2 and a capacitor C 1, the anode of described laser diode LD connects the drain electrode of MOSFET pipe, described first resistance R, 1 one termination LD drivers turn-off pin Txdis, the grid of another termination MOSFET pipe, described second resistance R 2 and capacitor C 1 formation charging and discharging circuit in parallel, an end ground connection in this loop, the grid of another termination MOSFET pipe, the source electrode of MOSFET pipe connects power Vcc.

The size of described first resistance R 1 and second resistance R 2 is 10K Ω～300K Ω, and capacitor C 1 is 1uF～10uF.

The resistance of described first resistance R 1 and second resistance R 2 is respectively: 100K Ω and 200K Ω, capacitor C 1 is 4.7uF.

Owing to increased slow start circuit in the above-mentioned drive circuit for laser, drive current in the time of can increasing the laser diode LD unlatching slowly, reduce laser temperature rising speed, reduced the wave length shift of laser, to the requirement of laser wavelength stability, met in the opening time 20ms of DWDM SFP multi-source agreement regulation the opening time of laser when meeting the dwdm system application.

Description of drawings

Fig. 1 represents the drive circuit for laser schematic diagram of the DWDM SFP integrated module of optical transceiver of prior art.

Fig. 2 represents the unlatching sequential schematic diagram of laser shown in Figure 1.

Fig. 3 represents the utility model drive circuit for laser schematic diagram.

Fig. 4 represents the drive circuit for laser schematic diagram that is provided with slow start circuit shown in Figure 3.

The unlatching sequential schematic diagram of Fig. 5 the utility model drive circuit for laser.

Embodiment

Drive circuit for laser as shown in Figure 3 comprises laser assembly TOSA10, and this assembly is integrated by LD11 and thermoelectric refrigerating unit TEC12, LD driver 20, TEC driver 30 and a slow start circuit 40 that is connected the LD11 anode.The improvement of this drive circuit is: increased a slow start circuit 40 on the basis of drive circuit for laser shown in Figure 1.

The drive circuit for laser that is connected with slow start circuit 40 as shown in Figure 4, this slow start circuit 40 comprises: MOSFET pipe, first resistance R 1, second resistance R 2 and a capacitor C 1, the anode of laser diode LD 11 connects the drain electrode of MOSFET pipe, the shutoff pin Txdis of first resistance R, 1 one termination LD drivers 20, the grid of another termination MOSFET pipe, second resistance R 2 and capacitor C 1 charging and discharging circuit that forms in parallel, the one end ground connection in this loop, the other end and the grid that connects the MOSFET pipe, the source electrode of MOSFET pipe connects power Vcc.This slow start circuit 40 utilizes the level of the shutoff pin Txdis of LD driver 20 to control the grid voltage of MOSFET pipe, and grid voltage slowly changes opens the MOSFET pipe, to reach the purpose that laser drive current slowly increases.It opens sequential chart as shown in Figure 5, and in t2 opening time section, turn-offing to the luminous power opening process from luminous power is the curve of a slow rising, can not produce the big electric current of burst, can effectively restrain the drift of laser wavelength.MOSFET is the SI2333DS P-channel field-effect transistor (PEFT) pipe of VISHAY company in this example, and the resistance that R1 and R2 are set is respectively 100K Ω and 200K Ω, capacitor C 1 is 4.7uF, the grid voltage that can make MOSFET is near threshold voltage, can make the MOSFET pipe after the level that turn-offs pin Txdis overturns, just get started conducting like this, and slowly open, increase channel current up to the laser operate as normal, at this moment, in the opening time is in the 15ms, the wave length shift of laser satisfies the requirement of DWDM SFP multi-source agreement fully in λ c-0.2nm～λ c+0.2nm scope.

Be described in detail with regard to the opening process and the turn off process of this circuit below laser:

One, laser opening process.The level of the shutoff pin Txdis of LD driver 20 jumps to low level by high level at this moment, and bias current path (Ibias) and modulated current path (Imod) are opened simultaneously.But this moment is because capacitor C 1 has been charged when being high at the level that turn-offs pin Txdis finishes, in the moment of the level saltus step of Txdis, the voltage on capacitor C 1 both sides can not suddenly change, make the grid of MOSFET pipe still be high level, the MOSFET pipe is in cut-off state, do not have electric current to flow through laser diode LD 11, this moment, laser was not luminous.Second resistance R, 2 discharges of 1 pair first resistance R 1 of capacitor C and shunt circuit subsequently, the grid voltage of MOSFET pipe reduces gradually, because the threshold voltage of P channel mosfet pipe is approximately than the low 0.7V of power source voltage Vcc, when its grid voltage during less than threshold voltage, MOSFET pipe beginning conducting, and along with the progressively reduction of grid voltage, the MOSFET pipe is operated in the variable resistor district gradually, the conducting electric current of MOSFET pipe increases gradually, up to being operated in normal condition.In order to guarantee that start-up course can not surpass 20ms, need reasonably to select the MOSFET grid voltage.If it is too many that grid voltage exceeds threshold voltage, under the influence of the cut-in voltage of MOSFET pipe, grid voltage drops to this section of threshold voltage change procedure from initial value will take the too many time of whole starting process, interior during this period of time MOSFET pipe all is in cut-off state fully, and laser is not luminous.If grid voltage is lower than threshold voltage, then laser can be opened luminously at once, does not reach the purpose that laser drive current slowly increases.The dividing potential drop of turn-offing pin Txdis level by first resistance R 1 and 2 pairs of second resistance R can reach the effect of regulating MOSFET tube grid voltage.

Two, laser shutdown process.When the level that turn-offs pin Txdis during from low transition to high level, capacitor C 1 begins charging.LD driver 20 turn-offs bias current path and modulated current path immediately, though this moment MOSFET pipe also not fully by, laser still can be realized turn-offing immediately.Slow start circuit causes the MOSFET pipe slowly to end turn-offing laser diode current without any influence, and laser still can effectively turn-off fast.

Claims

1. drive circuit for laser, comprise a laser assembly TOSA, this assembly is integrated by a thermoelectric refrigerating unit TEC and a laser diode LD, one LD driver, one TEC driver, its feature in, the anode of described laser diode LD connects a slow start circuit, this slow start circuit comprises: MOSFET pipe, first resistance (R1), second resistance (R2) and an electric capacity (C1), the anode of described laser diode LD connects the drain electrode of MOSFET pipe, described first resistance (R1) termination LD driver turn-offs pin Txdis, the grid of another termination MOSFET pipe, described second resistance (R2) and electric capacity (C1) formation in parallel charging and discharging circuit, an end ground connection in this loop, the grid of another termination MOSFET pipe, the source electrode of MOSFET pipe connects power Vcc.

2. drive circuit for laser according to claim 1 is characterized in that, the size of described first resistance (R1) and second resistance (R2) is 10K Ω～300K Ω, and electric capacity (C1) is 1uF～10uF.

3. drive circuit for laser according to claim 2 is characterized in that, the resistance of described first resistance (R1) and second resistance (R2) is respectively: 100K Ω and 200K Ω, electric capacity (C1) is 4.7uF.