CN203423694U

CN203423694U - Circuit capable of improving saturation optical power of APD light receiver

Info

Publication number: CN203423694U
Application number: CN201320452128.2U
Authority: CN
Inventors: 林少衡; 彭慧耀
Original assignee: Xiamen UX High Speed IC Co Ltd
Current assignee: Xiamen UX High Speed IC Co Ltd
Priority date: 2013-07-26
Filing date: 2013-07-26
Publication date: 2014-02-05
Anticipated expiration: 2023-07-26

Abstract

The utility model discloses a circuit capable of improving saturation optical power of an APD light receiver. The circuit is characterized by comprising a bias circuit, a monitoring circuit and a feedback module, wherein the bias circuit outputs a controlled bias voltage to the cathode of an APD and also comprises a control end capable of changing the bias voltage; the monitoring circuit is connected in series with the current loop of the APD and is provided with a monitoring end which monitors and outputs the photoelectric current value of the APD; and the feedback module is connected with the monitoring end through a sampling input end and is provided with a feedback output end capable of reflecting the over-current state of the monitoring end, the feedback output end being connected with the control end. By adopting the scheme, the photoelectric current of the APD does not exceed a set threshold so that the APD can receive signals with higher saturation optical power than by use of a conventional bias mode, and the restrictions for receiving optical power in an APD mode are extended.

Description

A kind of circuit that improves APD optical receiver saturated light power

Technical field

The utility model belongs to fiber optic communication field, relates to a kind of its control method of optical receiver and device of the APD of utilization photodiode.

Background technology

In optical fiber telecommunications system, in order to improve the receiving sensitivity index of receiving terminal receiver, often use the avalanche photodide (Avalanche Photo Diode, APD) based on avalanche multiplication effect, utilize its multiplier effect to improve the luminous sensitivity of receiver.APD pipe generally needs HVB high voltage bias (40-60V conventionally), and this HVB high voltage bias generally adopts DC BOOST circuit to boost to generate HVB high voltage bias, utilizes feedback control loop to maintain constant output high pressure.

Because APD has multiplication enlarge-effect, its multiplication factor is generally greater than 10, when input optical power is less, can amplify the response light electric current of photodiode, more than the optical receiver of therefore conventionally making of APD can improve 6dBm than the optical receiver sensitivity with PIN pipe is made.But when larger optical input power, equally also due to multiplication enlarge-effect, the photoelectric current of input trans-impedance amplifier also can be than being easier to reach receptible saturation photocurrent, therefore, therefore the saturated input optical power of the optical receiver of making of APD can be restricted, more than the low 6dBm of receiver that generally its saturated light power ratio is made by PIN photodiode.

Utility model content

The defect being restricted when optical input power is larger for the optical receiver of above-mentioned existing utilization APD photodiode, the utility model proposes a kind of circuit of the APD of raising optical receiver saturated light power, be intended to improve its input saturated light power, its technical scheme is as follows:

A circuit that improves APD optical receiver saturated light power, it comprises:

One biasing circuit, exports a controlled bias voltage in APD negative electrode; Also there is a control end that can change described bias voltage;

One supervisory circuit, is series in the current circuit of APD, has the photoelectricity flow valuve of real-time monitoring APD a monitoring client of output; And

One feedback module, is connected in described monitoring client by a sampling input; Have a feedback output end that can reflect described monitoring client over-current state, described feedback output end is connected with described control end.

The improver of this programme is as follows:

In preferred embodiment, described biasing circuit adopts DC BOOST structure, has an inductance, a switching device, a fly-wheel diode and a maintenance electric capacity; Wherein this inductance and fly-wheel diode forward are series in the current circuit of output cathode, and the current path of this switching device is series between this inductance and fly-wheel diode tie point and ground; Separately there is a voltage sampling network, be connected between described positive pole and ground, and obtain its voltage sampling and export from a sampling end; One first error amplifier, its output is controlled described switching device by a PWM modulation controller; Input of this first error amplifier connects respectively described sampling end, and another is described control end.

In preferred embodiment, described supervisory circuit comprises a mirror current source, and its input is connected in described positive pole, and its output is connected in APD negative electrode, and another output is described monitoring client.

In preferred embodiment, described feedback module comprises:

Sampling resistor R3, is connected between described monitoring client and ground;

The second error amplifier, its negative input end connects described monitoring client, and its positive input terminal connects a reference voltage terminal that produces reference voltage;

Adjust pipe M2, its grid connects the output of described the second error amplifier, drain as described feedback output end, and its source ground;

Controlling resistance R4, is connected between described reference voltage terminal and M2 drain electrode.

The beneficial effect of this programme has:

1. when larger luminous power input, the photoelectric current of APD can not surpass the threshold value of setting, thereby can make APD receive than the higher signal of traditional bias mode saturated light power, has expanded the restriction of APD mode received optical power.

2. when luminous power does not reach threshold value, still keep the multiplication enlarge-effect of APD, utilized substantially APD light receiving tube.

Accompanying drawing explanation

Below in conjunction with accompanying drawing embodiment, the utility model is described in further detail:

Fig. 1 is the method step schematic diagram of the utility model one embodiment;

Fig. 2 is circuit diagram embodiment illustrated in fig. 1.

Embodiment

As shown in Figure 1, the schematic diagram of an embodiment of the utility model, Fig. 2 is the physical circuit figure that realizes Fig. 1 method;

The present embodiment comprises the following steps:

Initialization step 1: an APD photodiode is arranged to a biasing circuit 100 and a supervisory circuit 20, this biasing circuit 100 provides the bias voltage of APD, it can be worked, simultaneously, biasing circuit 100 can the bias voltage of controlled change to APD, adjusts the bias state of APD.This supervisory circuit 20 is for monitoring in real time the photoelectric current of APD.

Threshold test step 2: set the threshold value of a photoelectric current, real-time APD photoelectric current size and this threshold of simultaneously supervisory circuit 200 being detected;

Discriminating step 3: by above-mentioned and comparison threshold value, check photoelectricity flow valuve whether within prefabricated scope, and draws two class results:

If A. APD photoelectric current is within this threshold range, carry out constant voltage step 4, in this step, biasing circuit 100 is set as the bias voltage of APD constant, then proceeds to threshold test step 2;

If B. APD photoelectric current surpasses this threshold range, enter pressure regulation step 5, in this pressure regulation step 5, biasing circuit 100 reduces bias voltage at once, then proceeds to threshold test step 2;

Above-mentioned steps can 2,3 and 4 can be summary responses, can be also multiple step format; The present embodiment adopts summary responses until APD photoelectricity flow valuve falls after rise in this threshold range again.Especially,, average light power more stable in order to realize maximizes, and in pressure regulation step 5, the photoelectric current of APD is clamped down in a steady state value.

Visible, when larger luminous power input, therefore biasing circuit 100 reduces the bias voltage of APD automatically, thereby reduce its multiplication constant, reduced the photoelectric current of final input trans-impedance amplifier, the photoelectric current of APD can not surpass the threshold value of setting, thereby can make APD receive than the higher signal of traditional bias mode saturated light power, has expanded the restriction of APD mode received optical power.On the other hand, when luminous power does not reach threshold value, still keep the multiplication enlarge-effect of APD, utilized substantially APD light receiving tube.

Shown in Fig. 2, the present embodiment also has other features:

Biasing circuit 100 puts on controlled bias voltage by supervisory circuit 20 negative electrode of APD pipe D2; And supervisory circuit 20 adopts in the current circuit that is series at APD pipe D2, monitor in real time the photoelectricity flow valuve of APD; Feedback module 200, is connected in biasing circuit 100 and supervisory circuit 20.

Feedback module 200 comprises a sampling input and a feedback output end 201, and this sampling input obtains APD photoelectric current is synchronously converted into a monitoring voltage, by sampling resistor R3, is connected in and between monitoring client 21 and ground, obtains this monitoring voltage.

Biasing circuit 100 adopts DC BOOST structure, has an inductance L 1, a switching device M1, a sustained diode 1 and a maintenance capacitor C 1; Wherein this inductance L 1 and sustained diode 1 forward are series in the current circuit of output cathode, the current path of switching device M1 is series between this inductance L 1 and sustained diode 1 tie point and ground, by the switching manipulation of switching device M1, realize voltage and VCC voltage Downward addition in inductance L 1, make the anodal high pressure that is suitable for APD pipe D2 that obtains.

One voltage sampling network, the concatermer of R1 and R2, is connected between positive pole and ground, and obtains its voltage sampling, from sampling end 101 output, i.e. links of R1 and R2; One first error amplifier 50, its output is by PWM modulation controller 10 control switch device M1; These the first error amplifier 50 two inputs connect respectively sampling end 101 and feedback output end 201, connect the control end that this feedback output end is this biasing circuit 100.

Feedback module 200 also comprises the second error amplifier 60, and its negative input end connects monitoring client 21, and its positive input terminal connects a reference voltage terminal 70 that produces reference voltage; Adjust pipe M2 for one, its grid connects the output of the second error amplifier 60, drain as feedback output end 201, and its source ground.Separately there is a controlling resistance R4, be connected between reference voltage terminal 70 and M2 drain electrode.

When APD manages D2 photoelectric current lower than threshold value, the stable reference voltage of this feedback output end 201 output one; When the rising of APD photoelectric current reaches threshold value, this feedback output end 201 reduces reference voltages; Simultaneously, the first error amplifier 50, according to the voltage comparative result of the magnitude of voltage of feedback output end 201 and sampling end 101, is controlled PWM modulation controller 10, to change bias voltage, make monitoring voltage and reference voltage, R1 and R2 tie point keep equating with feedback output end 201.

Be below the complete operating state of this circuit:

When the luminous power of input APD pipe D2 hour, the average light electric current that flows through APD is less, also less from the electric current of monitoring client 21 mirror images inflow pull down resistor R3 in supervisory circuit 20, when the voltage of monitoring client 21 is less than reference voltage terminal 70 voltage 1.25V, the second error amplifier 60 output 0 level, as the adjustment pipe M2 of current source, in cut-off state, no current flows through resistance R 4, therefore R4 does not produce pressure drop, and the reference voltage of inputting the first error amplifier 50 negative input ends equals 1.25V.Due to the feedback effect of the first error amplifier 50, the pressure drop of sampling end 101 will equal 1.25V, so the negative electrode of APD pipe D2 will be biased in constant high-pressure, and this high-voltage value is:

V _HIGH=1.25V*(R2+R1)/R2

When the luminous power of input APD pipe D2 increases gradually, the average light electric current of D2 also increases, the now pressure drop of R3 also progressively increases, while increasing to 1.25V, the average light electric current of thinking D2 has arrived a threshold value, now the second error amplifier 60 output voltages start to raise, adjusting pipe M2 progressively opens, R4 progressively has electric current to flow through and produces pressure drop, thereby the reference voltage of inputting the first error amplifier 50 secondary inputs also progressively reduces, by the effect of PWM modulation controller 10, adjust the DC BOOST feedback control loop of biasing circuit 100, the reverse bias voltage that is carried in APD pipe D2 negative electrode also will progressively reduce, D2 multiplication constant progressively reduces, thereby also corresponding reducing of the photoelectric current that flows through D2.By the autoregulation of whole feedback control loop, the average light electric current that flows through APD will be clamped down on for,

I _MAX=1.25V/R3

This current value can be along with input optical power continues to increase and increases, thereby widened saturated input optical power, finally, the trans-impedance amplifier 40 in TO-CAN module 30 still can receive the more input optical power information of wide region by D2 before saturation current state.

In this programme, feedback module 200 has a variety of execution modes, after this programme discloses, those skilled in the art can restructure voluntarily according to feedback module 200 and with the operation principle of biasing circuit 100, comprise that realizing monitoring client 21 voltages causes the circuit structure of feedback output end 201 variations and the mode that feedback module 200 is controlled biasing circuits 100, these changes, as long as apply to the principle of feedback module 200, belong to scheme identical or that be equal to.

The above, it is only the utility model preferred embodiment, therefore can not limit according to this scope that the utility model is implemented, the equivalence of doing according to the utility model the scope of the claims and description changes and modifies, and all should still belong in the scope that the utility model contains.

Claims

1. a circuit that improves APD optical receiver saturated light power, is characterized in that: it comprises:

2. a kind of circuit that improves APD optical receiver saturated light power according to claim 1, is characterized in that: described biasing circuit adopts DC BOOST structure, has an inductance, a switching device, a fly-wheel diode and and keeps electric capacity; Wherein this inductance and fly-wheel diode forward are series in the current circuit of output cathode, and the current path of this switching device is series between this inductance and fly-wheel diode tie point and ground; Separately there is a voltage sampling network, be connected between described positive pole and ground, and obtain its voltage sampling and export from a sampling end; One first error amplifier, its output is controlled described switching device by a PWM modulation controller; Input of this first error amplifier connects respectively described sampling end, and another is described control end.

3. a kind of circuit that improves APD optical receiver saturated light power according to claim 2, it is characterized in that: described supervisory circuit comprises a mirror current source, its input is connected in described positive pole, and its output is connected in APD negative electrode, and another output is described monitoring client.

4. according to a kind of circuit that improves APD optical receiver saturated light power described in claim 1 or 2 or 3, it is characterized in that: described feedback module comprises: