CN104991180A - Photoelectric detector assembly bandwidth detecting method and device - Google Patents

Abstract

The invention provides a photoelectric detector assembly bandwidth detecting method and a photoelectric detector assembly bandwidth detecting device. The photoelectric detector assembly bandwidth detecting device comprises a light source generator, an intensity modulator, a signal generator, an adjustable DC voltage source and a phase-locked amplifier, wherein an input end of the intensity modulator is respectively connected with an output end of the light source generator, an output end of the signal generator and an output end of the adjustable DC voltage source; an output end of the intensity modulator is connected with an input end of a detected photoelectric detector assembly; and an input end of the phase-locked amplifier is respectively connected with an output end of the detected photoelectric detector assembly and the output end of the signal generator. The technical scheme provided by the invention is simple in structure and convenient in operation, and improves the accuracy of the photoelectric detector assembly bandwidth detecting device.

Description

A kind of photodetector assembly bandwidth detection method and apparatus

Technical field

The present invention relates to a kind of detection method and device, specifically relate to a kind of photodetector assembly bandwidth detection method and apparatus based on phase lock amplifying technology.

Background technology

The effect of photodetector is that light signal is converted to electric signal, is mainly used in the fields such as Photoelectric Detection, Fibre Optical Sensor, optical fiber communication, luminous power metering.In optical current, voltage transformer (VT), in order to the characteristic of easy to use and better performance photodiode PIN, usually by photodiode and prime amplifier integrated, composition photodetector assembly PIN-FET.This assembly takes full advantage of the high input impedance charcteristic of field effect transistor FET, the photocurrent that photodiode PIN exports is converted to voltage signal, reduce external disturbance and stray capacitance simultaneously, greatly reduce thermonoise, detect significant to noiselike signal.

Optical current, voltage transformer (VT) adopt interfere measurement technique, are realized the measurement of primary current, voltage by the phase differential measured between two bundle coherent lights.In signal transacting, adopt digital closed loop signal detection technique, there is the advantages such as the linearity is high, dynamic range is large, have important application in intelligent substation, extra-high voltage AC and DC field of power transmission.

Digital closed loop signal detecting method, based on phase-modulation, demodulation techniques, by the tested current-modulation of direct current or power frequency on a high frequent signal, avoids the impact of low frequency 1/f noise.Introduce after phase-modulation, interference light intensity becomes high-frequency square-wave signal, is to ensure measuring accuracy, needs photodetector to have very wide bandwidth, thus switching signal without distortion.

Therefore, provide a kind of photodetector assembly frequency characteristic pick-up unit and method, accurately grasp the bandwidth characteristic of photodetector assembly, for the realization of digital closed loop signal detection technique and performance boost significant.

Summary of the invention

In order to solve the problems referred to above existing in prior art, the invention provides a kind of photodetector assembly bandwidth detecting device.

Technical scheme provided by the invention is: a kind of photodetector assembly bandwidth detecting device, comprises light source generator, intensity modulator, signal generator, adjustable direct voltage source and lock-in amplifier; Its improvements are: the input end of described intensity modulator is connected with the output terminal of described adjustable direct voltage source with the output terminal of described light source generator, the output terminal of described signal generator respectively; The output terminal of described intensity modulator is connected with the input end of tested photodetector assembly; The input end of described lock-in amplifier is connected with the output terminal of described tested photodetector assembly and the output terminal of described signal generator respectively.

Preferably, the light that described light source generator sends enters described photodetector assembly through intensity modulator, described adjustable direct voltage source and described signal generator export DC offset voltage signal and Sine Modulated voltage signal respectively to intensity modulator, to change the sinusoidal light wave signal that described intensity modulator exports photodetector to; Described photodetector assembly exports with described sinusoidal light wave signal with voltage signal frequently extremely described lock-in amplifier; The Sine Modulated voltage signal that described signal generator exports exports described lock-in amplifier to as reference signal simultaneously; Described lock-in amplifier exports the voltage signal be directly proportional to the output voltage signal amplitude of described photodetector assembly.

Preferably, described lock-in amplifier is the lock-in amplifier with orthogonal phase-locked function.

Preferably, described light source generator is the light source generator carrying driving circuit.

Further, described light source generator is any one in laser instrument, super-radiance light emitting diode or erbium-doped fiber optic source generator.

Further, described intensity modulator is M-Z interfere type LiNbO ₃intensity modulator.

Another object of the present invention is to provide a kind of photodetector assembly bandwidth detection method, described method comprises the steps:

(1) apply bias voltage with adjustable direct voltage source in the DC port of intensity modulator, regulate continuously from small to large, bias voltage value v corresponding when recording light electric explorer output voltage is minimum and maximum respectively _minand v _max, get the equal threshold voltage of the two be applied in intensity modulator;

(2) apply sinusoidal modulation signal with signal generator at the prevention at radio-frequency port of intensity modulator, ensure that the amplitude of sinusoidal modulation signal is constant, continuous conditioning signal frequency, and record the output voltage of lock-in amplifier; Gain R (f) of photodetector assembly is calculated, using the bandwidth of signal frequency corresponding during gain R (f) decline 3dB as tested photodetector assembly according to output voltage.

8, detection method as claimed in claim 7, is characterized in that: the output voltage of described lock-in amplifier comprises the output voltage V with reference voltage homophase ₁(f) and the output voltage V orthogonal with reference voltage ₂(f); Gain R (f) of photodetector assembly is obtained by following formulae discovery:

$R\left(f\right)=\frac{2V_{\mathrm{\π}}}{{\mathrm{\πI}}_0{V}_0^2}\sqrt{V_1{\left(f\right)}^2+V_2{\left(f\right)}^2}$

Wherein: I ₀for light source output intensity, V _πfor the half-wave voltage of intensity modulator, V ₀for the amplitude of modulation voltage, f is signal frequency.

Compared with immediate technical scheme, the present invention has following marked improvement:

1) photodetector assembly bandwidth detecting device structure provided by the invention is simple, easy to operate, utilizes the noise inhibiting ability of lock-in amplifier, improves the measuring accuracy of photodetector assembly bandwidth detecting device.

2) the present invention adopts M-Z interfere type LiNbO ₃intensity modulator realizes light intensity to be changed according to frequency, and with additive method such as directly modulation method, electro-absorption modulation method etc. is compared, M-Z interfere type LiNbO ₃the responsive bandwidth of intensity modulator is very high, and usually at more than 100MHz, far away higher than tested photodetector assembly, systematic error during measurement is negligible, improves the accuracy of measurement of photodetector assembly bandwidth detecting device.

3) the present invention adopts the lock-in amplifier possessing orthogonal phase-locked function, homophase and orthogonal two-way output signal can be detected in use simultaneously, and then utilize homophase and orthogonal two-way output signal to calculate gain R (f) of photodetector assembly, calculate gain R (f) under this mode not by the impact of tested photodetector assembly phase delay, improve the accuracy of photodetector assembly bandwidth detection.

4) bias voltage applied in the DC port of intensity modulator get photodetector output voltage minimum and maximum time corresponding bias voltage value v _minand v _maxaverage: the light intensity change that Sine Modulated voltage can be made to cause is the most obvious, and during measurement, signal to noise ratio (S/N ratio) is maximum, improves measuring accuracy.

Accompanying drawing explanation

Fig. 1 is the hardware configuration schematic diagram of photodetector assembly bandwidth detecting device provided by the invention.

Embodiment

In order to understand the present invention better, below in conjunction with Figure of description and example, content of the present invention is described further.

The structural representation of photodetector assembly bandwidth detecting device provided by the invention as shown in Figure 1.Comprise light source generator, intensity modulator, adjustable direct voltage source, signal generator and lock-in amplifier.

(1) light source generator: light source generator is the light source generator carrying driving circuit can be any one in laser instrument, super-radiance light emitting diode or erbium-doped fiber optic source generator; The output terminal of light source generator is connected with the input end of intensity modulator, and the light that light source generator sends inputs to tested photodetector assembly after intensity modulator modulation.

(2) adjustable direct voltage source: adjustable direct voltage source is all purpose instrument equipment, its output terminal is connected with the DC voltage input end mouth of intensity modulator, for to intensity modulator input direct-current bias voltage, the Sine Modulated voltage acting in conjunction that this DC input voitage and signal generator produce, thus change the output intensity of intensity modulator.

(3) signal generator: signal generator is all purpose instrument equipment, the sine voltage signal that signal generator exports enters intensity modulator and lock-in amplifier respectively as Sine Modulated voltage signal and reference signal; Sine Modulated voltage signal and the acting in conjunction of DC offset voltage signal, change the output voltage of intensity modulator;

(4) intensity modulator: intensity modulator is M-Z interfere type LiNbO3 intensity modulator, its effect changes output intensity by changing impressed voltage (DC offset voltage, Sine Modulated voltage); Adopt LiNbO3 type electro-optic intensity modulator to realize light intensity in the present invention to change according to frequency, than additive method (as adopted directly modulation method, electro-absorption modulation method etc.), advantage of the present invention is very high with the responsive bandwidth of LiNbO3 type modulator, usually at more than 100MHz, far away higher than tested photodetector assembly, make the systematic error introduced during measurement negligible, the accuracy of measurement is higher.

Suppose that the DC offset voltage that adjustable direct voltage source is input to intensity modulator is V _bias; The Sine Modulated voltage that signal generator is input to intensity modulator is V _m, V _m=V ₀sin (2 π ft), wherein V ₀for the amplitude of modulation voltage, f is modulating frequency, and t is time variable; The light intensity that light source generator is input to intensity modulator is I ₀; Then intensity modulator exports I (t):

$I\left(t\right)=\frac{I_0}{2}\{1+cos\[\left(\frac{V_m-V_{bias}}{V_{\mathrm{\π}}}\right)\mathrm{\π}\]\}---\left(1\right)$

Wherein: V _πfor the half-wave voltage of intensity modulator.Work as V _bias=V _πwhen/2, above formula becomes:

$\begin{array}{c}I\left(t\right)=\frac{I_0}{2}\[1+cos(\frac{V_m}{V_{\mathrm{\π}}}\mathrm{\π}-\frac{\mathrm{\π}}{2})\]=\frac{I_0}{2}\[1+\sin \left(\frac{V_m}{V_{\mathrm{\π}}}\mathrm{\π}\right)\]\\ =\frac{I_0}{2}\{1+\sin \[\frac{V_0}{V_{\mathrm{\π}}}\mathrm{\π}\sin \left(2\mathrm{\π}ft\right)\]\}\end{array}---\left(2\right)$

Wherein: V ₀<<V _π; Formula (2) is equivalent to: $I\left(t\right)=\frac{I_0}{2}(1+\frac{V_0}{V_{\mathrm{\&pi;}}}\mathrm{\&pi;}sin2\mathrm{\&pi;}ft)---\left(3\right)$

Tested photodetector assembly: the input end of tested photodetector assembly is connected with the output terminal of intensity modulator, its output terminal is connected with the input end of lock-in amplifier.It is a device that will input that light intensity I (t) becomes output voltage V (t), and wherein V (t) and I (t) exist following relation: V (t)=R (f) * I (t)+V _b(4)

Wherein R (f) the opto-electronic conversion gain that is photodetector assembly, it be one with modulating frequency f change the function of change, represent the amplitude versus frequency characte of photodetector assembly, V _bfor the bias voltage of photodetector assembly, refer to the output voltage of detector assembly when luminous power is 0, V _bbe a fixing value, it is only relevant with photodetector assembly itself.

Consider that light intensity I (t) has phase delay after being input to photodetector assembly, formula (4) can be changed into:

Wherein for the phase delay that photodetector is introduced; Photodetector output voltage V (t) through exporting lock-in amplifier to after straight process; Being by the DC component filtering in V (t) every straight process, only retaining AC compounent: V (t) through becoming after directly processing:

(5) lock-in amplifier: lock-in amplifier is the lock-in amplifier with orthogonal phase-locked function, its input end is connected with the output terminal of photodetector assembly, for receiving output voltage V (t) of photodetector assembly; Another input end is connected with the output terminal of signal generator, for the reference voltage that Received signal strength generator exports; The reference voltage that lock-in amplifier can export according to output voltage V (t) of photodetector assembly and signal generator demodulates the in-phase voltage V with reference voltage homophase in V (t) ₁(f) and the quadrature voltage V orthogonal with reference voltage ₂f () also exports:

Utilize the homophase output voltage V of lock-in amplifier further ₁(f) and quadrature output voltage V ₂(f), simultaneous formula (7) and (8), according to gain R (f) of photodetector assembly can be calculated:

$R\left(f\right)=\frac{2V_{\mathrm{\&pi;}}}{{\mathrm{\&pi;I}}_0{V}_0^2}\sqrt{V_1{\left(f\right)}^2+V_2{\left(f\right)}^2}---\left(9\right)$

The phase retardation of the R (f) calculated by formula (9) and photodetector assembly irrelevant, not by the impact of photodetector component delays phase place, the accuracy of measurement of photodetector assembly bandwidth can be improved.

The method utilizing the pick-up unit in Fig. 1 to detect photodetector assembly bandwidth comprises two steps:

S1: apply bias voltage with adjustable direct voltage source in the DC port of intensity modulator, regulate continuously from small to large, bias voltage value v when recording light electric explorer output voltage is minimum and maximum respectively _minand v _max, get the equal threshold voltage of the two be applied in intensity modulator, now the lucky corresponding pi/2 phase bias of bias voltage; The light intensity change that this value of bias voltage can make Sine Modulated voltage cause is the most obvious, measures signal to noise ratio (S/N ratio) maximum.

S2: apply sinusoidal modulation signal at the prevention at radio-frequency port of intensity modulator with signal generator, ensures that the amplitude of sinusoidal modulation signal is constant, continuous conditioning signal frequency, and records the output voltage of lock-in amplifier: comprise homophase output voltage V ₁(f) and quadrature output voltage V ₂f (), utilizes formula (9) according to homophase output voltage V ₁(f) and quadrature output voltage V ₂f () calculates gain R (f) of photodetector assembly, using the bandwidth of signal frequency corresponding during gain R (f) decline 3dB as tested photodetector assembly.

These are only embodiments of the invention, be not limited to the present invention, within the spirit and principles in the present invention all, any amendment made, equivalent replacement, improvement etc., all applying within the right of the present invention awaited the reply.

Claims (8)

1. a photodetector assembly bandwidth detecting device, comprises light source generator, intensity modulator, signal generator, adjustable direct voltage source and lock-in amplifier; It is characterized in that: the input end of described intensity modulator is connected with the output terminal of described adjustable direct voltage source with the output terminal of described light source generator, the output terminal of described signal generator respectively; The output terminal of described intensity modulator is connected with the input end of tested photodetector assembly; The input end of described lock-in amplifier is connected with the output terminal of described tested photodetector assembly and the output terminal of described signal generator respectively.

2. pick-up unit as claimed in claim 1, it is characterized in that: the light that described light source generator sends enters described photodetector assembly through intensity modulator, described adjustable direct voltage source and described signal generator export DC offset voltage signal and Sine Modulated voltage signal respectively to intensity modulator, to change the sinusoidal light wave signal that described intensity modulator exports photodetector to; Described photodetector assembly exports with described sinusoidal light wave signal with voltage signal frequently extremely described lock-in amplifier; The Sine Modulated voltage signal that described signal generator exports exports described lock-in amplifier to as reference signal simultaneously; Described lock-in amplifier exports the voltage signal be directly proportional to the output voltage signal amplitude of described photodetector assembly.

3. pick-up unit as claimed in claim 1, is characterized in that: described lock-in amplifier is the lock-in amplifier with orthogonal phase-locked function.

4. pick-up unit as claimed in claim 1, is characterized in that: described light source generator is the light source generator carrying driving circuit.

5. pick-up unit as claimed in claim 4, is characterized in that: described light source generator is any one in laser instrument, super-radiance light emitting diode or erbium-doped fiber optic source generator.

6. pick-up unit as claimed in claim 1 or 2, is characterized in that: described intensity modulator is M-Z interfere type LiNbO ₃intensity modulator.

7., by the photodetector assembly bandwidth detection method that the pick-up unit described in claim 1 or 2 realizes, it is characterized in that: described method comprises the steps:

(1) apply bias voltage with adjustable direct voltage source in the DC port of intensity modulator, regulate continuously from small to large, bias voltage value v corresponding when recording light electric explorer output voltage is minimum and maximum respectively _minand v _max, get the equal threshold voltage of the two be applied in intensity modulator;

(2) apply sinusoidal modulation signal with signal generator at the prevention at radio-frequency port of intensity modulator, ensure that the amplitude of sinusoidal modulation signal is constant, continuous conditioning signal frequency, and record the output voltage of lock-in amplifier; Gain R (f) of photodetector assembly is calculated, using the bandwidth of signal frequency corresponding during gain R (f) decline 3dB as tested photodetector assembly according to output voltage.

8. detection method as claimed in claim 7, is characterized in that: the output voltage of described lock-in amplifier comprises the output voltage V with reference voltage homophase ₁(f) and the output voltage V orthogonal with reference voltage ₂(f); Gain R (f) of photodetector assembly is obtained by following formulae discovery:

$R\left(f\right)=\frac{2V_{\mathrm{\&pi;}}}{{\mathrm{\&pi;I}}_0{V}_0^2}\sqrt{V_1{\left(f\right)}^2+V_2{\left(f\right)}^2}$

Wherein: I ₀for light source output intensity, V _πfor the half-wave voltage of intensity modulator, V ₀for the amplitude of modulation voltage, f is signal frequency.