CN202177841U - Numerical control type automatic program control (APC) module for burst mode laser driver - Google Patents

Abstract

The utility model discloses a numerical control type automatic program control (APC) module for a burst mode laser driver, which comprises a reference source generating circuit, a current amplifying and comparing circuit, a controlled bias current source, a modulating current source and a switch current module. The current amplifying and comparing circuit comprises a current amplifying circuit, a comparator, a digital filter, a logic control unit, a bias current meter checking register, a latch, a resistor (R1), a capacitor (C1), a first switch (S1), a second switch (S2) and a third switch (S3). The technical scheme adopted by the APC module establishes a quick start-up process and a corresponding state maintenance mechanism, reduces bias current establishment time in a burst transmission period and improves transmission efficiency of the data.

Description

A kind of digital control type APC module that is used for the burst mode laser driver

Technical field

The utility model relates to a kind of circuit of laser driver, especially a kind of digital control type APC module that is used for the burst mode laser driver

Background technology

Along with the appearance of multiple access optical-fiber network, time division multiplex (TDMA) technology is introduced in the optical fiber multiple spot in the one point data transmission system.Under this technology, each transmitter only activates and sends data in the time period that allows separately.Like this, data transmit with the form of packet, and this tranmission techniques is called as burst mode.Upload a kind of communication means of data stream as the optical network unit (ONU) of multiple spot to the optical line terminal (OLT) of single-point, TDMA is applied in the EPON (PON).In tdma system, for laser drive circuit following specific (special) requirements is arranged: (1) idle state, the laser driver that the ONU end sends data will turn-off when unactivated state, blocks the light signal that sends through laser instrument.Otherwise nonactivated a plurality of ONU have residual light signal to a certain degree, can add up at the OLT end, and normal data-signal is produced catastrophic destruction.(2), in the cycle that each burst transmits, all need automated power control (APC) module can set up/recover the bias current of laser instrument fast for each ONU.Otherwise, in limited Burst Period, can not accomplish effective transmission of data.And typical A PC module (as shown in Figure 1) is in the cycle that burst transmits at present, and the foundation that requires a great deal of time and setover reduces data transmission efficiency.

Summary of the invention

For overcoming above shortcoming, the utility model provides a kind of digital control type APC module that is used for the burst mode laser driver that can reduce the bias current Time Created in the burst transmission cycle.

In order to reach above goal of the invention, the utility model provides a kind of digital control type APC module that is used for the burst mode laser driver, comprises the benchmark source generating circuit; Electric current amplifies and comparator circuit, controlled bias current source, modulation current source; The switching current module, wherein

Said electric current amplifies and comparator circuit comprises current amplification circuit, comparer, digital filter, logic control element, the bias current register of tabling look-up, latch, and resistance (R1), electric capacity (C1), first switch (S1), second switch (S2), the 3rd switch (S3);

The output terminal of said current amplification circuit connects an end of the 3rd switch (S3); The 3rd switch (S3) other end connects an end, an end of resistance (R1), an end of electric capacity (C1) and the negative input end of said comparer of second switch (S2); The other end of second switch (S2) connects the Iref end of benchmark source generating circuit; The other end of resistance (R1) connects an end of first switch (S1); The other end of first switch (S1) connects the Vref end of benchmark source generating circuit and the positive input terminal of comparer, the other end ground connection of electric capacity (C1);

The output terminal of said comparer is connected with the input end of said digital filter; The output terminal of an input end linking number character filter of logic control element; Another input end links to each other with external timing signal; An output terminal of logic control element connects a table look-up end of register of said bias current; Another output terminal connects external data modulation module, and the table look-up other end of register of bias current connects the input end of said latch, and the output terminal of latch connects outside direct current biasing module.

The laser driver that has adopted the disclosed digital control type APC of the utility model module is after obtaining the APC enable signal; Accomplish a quick start-up course earlier---promptly pass through three phases; Fast the bias current of laser instrument is drawn high required current value fast, and keep the control signal of this bias current through latch; Data transmitting period is fast quick-recovery laser bias current on the basis of the control signal that latchs; And can, each, accomplish control in happening suddenly the transmission cycle to laser bias current with digital filtering mode through the comparer monitoring.This quick start-up course and corresponding state keep mechanism; Make the APC module of the utility model satisfy two requirements of the drive circuit for laser of describing in the background technology; Reduce the bias current Time Created in the burst transmission cycle, improve data transmission efficiency.

Description of drawings

Fig. 1 is at present typical burst mode laser driver APC module diagram

Fig. 2 is the disclosed a kind of digital control type APC module that is used for the burst mode laser driver of the utility model.

Fig. 3 has adopted the laser driver of the disclosed APC module of the utility model to open sequential chart

Embodiment

In order to understand the technical scheme of the utility model better, below through embodiment particularly and combine accompanying drawing at length to explain:

As shown in Figure 2, the disclosed digital control type APC module diagram that is used for the burst mode laser driver of the utility model comprises the benchmark source generating circuit, and electric current amplifies and comparator circuit; The controlled bias current source, modulation current source, the switching current module, wherein electric current amplification and comparator circuit comprise current amplification circuit; Comparer, digital filter, logic control element, the bias current register of tabling look-up; Latch, and resistance (R1), electric capacity (C1); First switch (S1), second switch (S2), the 3rd switch (S3).

The digital filter here, logic control element, the bias current register of tabling look-up, latch, R1, C1 are the nucleus modules of the utility model, also are the important improvement that is different from typical module.Because major part is a digital module, so this is referred to as digital control type APC module.

Digital filter receives the output (logic ' H '/' L ' level) of comparer.In the regular hour window, the output of comparer was sampled according to certain sampling period, relatively ' H ', the number of ' L ' is poor, sends comparative result to logic control element.

Logic control element is equivalent to a little cpu, is controlling the work of whole APC.Concrete is exactly to coordinate control APC at forbidding, enables beginning, and the work that bursty data transmits and the laser instrument of non-Burst Period ends.In quick start-up course,, bias current is drawn high expectation value fast according to set algorithm.In the burst transmission cycle, receive the output of digital filter, according to certain algorithm, with ' H ', the number difference of ' L ' converts certain bias current control signal (by means of the cooperation of bias current register) to, thus the control bias current reaches expectation value.Can guarantee that like this bias current is constant, and is clean in the time window scope.If exist than big-difference, can, next time window revise when beginning with respect to expectation value.

The bias current register of tabling look-up as its name suggests, is exactly a register, and internal storage the control signal of numerous bias currents, carries out bias current control to cooperate logic control element.

Latch receives from the table look-up output of register of bias current, latchs and send to controlled bias current sources, accomplishes the control task of bias current.

Resistance R 1 is the difference with reference current source Iref and current amplifier output current, on resistance R 1, converts the voltage difference with respect to reference voltage source Vref into, as comparator input terminal.

Capacitor C 1, in the non-burst transmission cycle, top crown is unsettled, with the voltage that keeps last one-period.Being beneficial to following one-period recovers fast.

Below, will specifically introduce the control action of the utility model in laser driver according to sequential shown in Figure 3:

One.

is ' H '; APC does not work, and bias current sources Ibias and modulation current source Imod are in disabled status---there is not output current.Also no-output of laser instrument then.And latch emptied.

Two.

becomes ' L ' by ' H ', and APC gets into quick start-up course:

Stage 1.Data path is by the signal cutout of logic control element, the input short circuit of current switch module, and receive on the biased electrical pressure point, two outputs of current switch modulating current reach balance, and the electric current that has Imod/2 flows into laser instrument.

The stages 2. logic control element control bias current register of tabling look-up is exported a bias current control signal, corresponds to bias current output size and is A.

Next, on the basis of A, with frequency Fclk, bias current begins to add up according to the B step-length, and the electric current of surveying the photoelectric diode of keeping watch on usefulness up to comparer surpasses the reference current Iref that expects.Because there is certain delay in the electric current foundation of being coupled on the photodiode from being established to of bias current, so bias current has certain overshoot with respect to expectation value.Need next stage to continue adjustment.

The time window of stages 3. digital filter is set at n * 1/Fclk (D among the figure); On the basis in stage 2; The decline C of elder generation; Cooperate logic control element to carry out the digital expectation average power of approaching through backfeed loop afterwards, in maximum eight steps, bias current is set on the expectation value quickly and accurately.The time window that amplifies can carry out counteracting to a certain degree with the time-delay of feedback.

After the completion, the conducting of Data path, the control of bias current are also transferred to more low-frequency APC loop and are controlled that (time window of digital filter is set at N * 1/Fclk, N＞n).

Note: the stage 1 and 2 takes place in fact simultaneously, the precedence on having no time.But, be divided into two stages here in order to set forth conveniently.

Three.

is the non-quick start-up course of ' L '; If BEN is ' H '; Laser driver should be in burst transmission cycle---Data transmit stage, and bias current sources Ibias and current switch output current (Data modulating current) are received laser driver.Owing to kept last one-period the bias current control signal Bias_ctrl of (might be quick startup, also possibly be the burst transmission cycle) on the latch, so can just can quickly recover to the bias current of one-period at Burst Period at the beginning just.Because the maintenance current potential effect of C1 at Burst Period at the beginning just, can let comparer export balance, can not cause bias current overshoot (overshot) simultaneously because of the time-delay in gallon loop.Bias current just begins to transmit valid data after setting up, and promptly modulating current is delivered on the laser driver under the control of Data input, thereby accomplishes the transmission of data.

Four.

is the non-quick start-up course of ' L '; If BEN is ' L '; Then not at burst mode in the cycle; The laser driver forbidding is realized through bias current sources Ibias is broken off to being connected of laser driver with current switch output current (Data modulating current).The reference current output (Iref) that keeps the benchmark source generating circuit simultaneously, the output of current amplifier, and resistance R 1, all the negative input end with comparer breaks off, thereby lets C1 maintain this current potential of one-period.And let latch pin the bias current control signal (Bias_Ctrl) of last one-period.

Those of ordinary skill in the art will be appreciated that; Above embodiment is used for explaining the present invention; And be not to be used as qualification of the present invention; As long as in connotation scope of the present invention, all will drop in claims scope of the present invention variation, the modification of the above embodiment.

Claims (1)

1. a digital control type APC module that is used for the burst mode laser driver comprises the benchmark source generating circuit, and electric current amplifies and comparator circuit, the controlled bias current source, and modulation current source, the switching current module is characterized in that:

Said electric current amplifies and comparator circuit comprises current amplification circuit, comparer, digital filter, logic control element, the bias current register of tabling look-up, latch, and resistance R 1, capacitor C 1, the first switch S 1, second switch S2, the 3rd switch S 3;

The output terminal of said current amplification circuit connects an end of the 3rd switch S 3; The 3rd switch S 3 other ends connect an end, an end of resistance R 1, an end of capacitor C 1 and the negative input end of said comparer of second switch S2; The other end of second switch S2 connects the Iref end of benchmark source generating circuit; The other end of resistance R 1 connects an end of first switch S 1, and the other end of first switch S 1 connects the Vref end of benchmark source generating circuit and the positive input terminal of comparer, the other end ground connection of capacitor C 1;

The output terminal of said comparer is connected with the input end of said digital filter; The output terminal of an input end linking number character filter of logic control element; Another input end links to each other with external timing signal; An output terminal of logic control element connects a table look-up end of register of said bias current; Another output terminal connects external data modulation module, and the table look-up other end of register of bias current connects the input end of said latch, and the output terminal of latch connects outside direct current biasing module.

Images