CN105960045A - Realization method and device of communication illumination sharing system based on LED high illumination efficiency - Google Patents

Abstract

The invention discloses a realization method and device of a communication illumination sharing system based on LED high illumination efficiency. The realization method is characterized in that a communication scheme of multi-element pulse falling edge coding is adopted, the charging and discharging frequency of an LED junction capacitor is reduced, the power consumed by charging and discharging is also reduced, and the illumination efficiency is improved; and a variable-length code element width is utilized, the duration time of the low level of driving signals is shortened, the duty ratio of the driving signals is increased, and the illumination brightness is improved. A sending end utilizes the multi-element coding method, n bits of transmission data are divided into one group, the code values of the groups of data are corresponding to different pulse falling edge positions, the signal pulse immediately rises as fast as possible after the signal pulse falls, and the transmission of the next code element is carried out; and a receiving end uses a received pulse rising edge as a time reference point, and the corresponding code values are recovered according to the positions of the falling edges, and data transmission is completed.

Description

The implementation method of communication illumination sharing system based on LED high illumination efficiency and device

Technical field

The present invention relates to LED-based visible light communication and lighting field, illuminate implementation method and the device of sharing system more particularly, to communicating of a kind of LED-based high illumination efficiency.

Background technology

White light LEDs has the energy-saving and environment friendly advantage such as efficiently as a kind of semiconductor light source, the most gradually substitutes conventional incandescent, fluorescent lamp, and high-voltage gas discharging light becomes the light source of 21 century most prospect.It is high, to features such as eye-safes that on the one hand white light LEDs has emission effciency；On the other hand, there is the advantages such as response speed is fast, modularity is good.Along with White-light LED illumination is promoted, people begin to focus on visible light communication based on white light LEDs, white LED lamp not only used chamber's intraoral illumination, and the white light that available LED sends, and define a kind of short-distance wireless optical communication link.A lot of scholars propose indoor visible light communication based on illuminating white light LEDs (VLC visible-light communication) system.White light LEDs is modulated the signal of telecommunication of transmission information is converted to optical signal by controller, the mode utilizing white light LEDs light-illuminating realizes indoor wireless transmission, optical receiving device is installed in the range of white light LEDs light-illuminating simultaneously, convert optical signals to the signal of telecommunication, set up visible ray wireless communication system, it is achieved the transmission of information.Compared with traditional radio communication and other wireless communication system, it is seen that it is high that optical communication technique has transmitting power, is not take up radio-frequency spectrum, without electromagnetic interference and electromagnetic-radiation-free, save the advantages such as the energy.Visible light communication technology has become as multiple countries study hotspot at present, but most of under test, although total system has realized, but also have with a certain distance from the practical stage, the property indices of system needs to be improved further, it is achieved scheme is also required to the most perfect.

One of problem that presently, there are is the excessive power drain problem that LED junction electric capacity causes:

The transmission medium of visible light communication is free space, bigger for the angle of divergence of the LED light emitting diode of illumination, and therefore the geometry loss of signal transmission is relatively big, and the signal eventually arriving at receptor is far smaller than transmitting terminal.Although it has been reported the transfer rate experimental system more than 1Gbt/s, but the distance realizing high-speed transfer only having several centimetres.

When communication distance becomes big, loss of signal is serious, and the bit error rate rises, and cannot reach require that of signal transmission.The distance of transmission to be improved needs to increase the power launching signal, i.e. increases the luminous power output of LED, this light-emitting area being accomplished by increasing LED, and the increase of area, the junction capacity causing device increases, and frequency response characteristic declines, and maximum communication rate is restricted again.Being the most singly LED component, the power characteristic of all semiconductor device and frequency characteristic contradiction on a device design, is the problem of the most all semiconductor device design persons institute facing.Current report both domestic and external also can not take into account two aspect performances, it is contemplated that can not solve at short notice, can only improve to a certain extent.

On the basis of existing LED component, being improved the response speed of system by external drive circuit, it is achieved high-speed communication, common scheme is to use preemphasis or equilibrium.But, owing to the junction capacity of illuminating LED is the biggest, in the magnitude of nF, High-speed driving signals will produce bigger power consumption to the discharge and recharge of this electric capacity, thus reduces the luminous efficiency of illuminator.There is presently no a scheme that can preferably solve the excessive power drain problem that LED junction electric capacity causes.

Additionally, employing pulse drive signal, if keeping signal peak-peak in the range of the rated current of LED, then, average current is inevitably less than the rated operational current of LED, causes brightness of illumination to decline；If brightness of illumination to be kept is constant, then need to keep average current to be much larger than the rated current of LED equal to rated operational current, i.e. peak point current.Owing to LED is when big electric current, luminous power can approach to saturation, and causes luminous efficiency to decline, and excessive peak point current, may cause the reduction of LED life.

Summary of the invention

In order to overcome above-mentioned the deficiencies in the prior art, present invention firstly provides the implementation method of a kind of communication illumination sharing system based on LED high illumination efficiency.

The present invention also propose a kind of based on LED high illumination efficiency communication illumination sharing system realize device.

For solving above-mentioned technical problem, technical scheme is as follows:

A kind of implementation method of communication illumination sharing system based on LED high illumination efficiency,

At transmitting terminal, data to be transmitted is merged encoder by n position and is divided into the data set of one group, n position, data set is converted into polynary trailing edge coding signal by pattern generator, and polynary trailing edge coding signal, after analog line driver amplifies, drives LED emission to produce optic communication signal；

At receiving terminal, optical-electrical converter receives optic communication signal, through the judgement of comparator, recovers polynary trailing edge coding signal, then decodes through decoder, obtain n-bit data group, then recovered data to be transmitted by data recovery circuit.

Preferably, at transmitting terminal, when every data transfer starts, data to be transmitted signal rises to high level from low level, and rising edge is as time reference, n position merges encoder and every for signal to be transmitted n position is divided into one group, according to often organizing the value of data, the pulse signal of output different in width, the pulse signal trailing edge moment is corresponding with the value of data to be transmitted: set the minimum slot time of pulse as τ, the value of n-bit data is x, then the width of pulse is (x+1) τ.

Preferably, after n position merges encoder output low level, rise immediately, carry out the transmission of next code element, so the length of each code element is change.

A kind of based on LED high illumination efficiency communication illumination sharing system realize device, encoder, pattern generator, analog line driver, LED, optical-electrical converter, comparator, decoder and data recovery circuit is merged including n position, data to be transmitted is merged encoder by n position and is divided into the data set of one group, n position, data set is converted into polynary trailing edge coding signal by pattern generator, polynary trailing edge coding signal, after analog line driver amplifies, drives LED emission to produce optic communication signal；Optical-electrical converter receives optic communication signal, through the judgement of comparator, recovers polynary trailing edge coding signal, then decodes through decoder, obtain n-bit data group, then recovered data to be transmitted by data recovery circuit.

Compared with prior art, the invention has the beneficial effects as follows:

1, use the communication plan of multi-pulse trailing edge coding, decrease the discharge and recharge number of times of LED junction electric capacity, thus decrease because the power of discharge and recharge consumption, improve illumination efficiency；

2, use the scheme that low level time is fixing, improve the dutycycle driving signal, improve the life-span of brightness of illumination and LED.

Accompanying drawing explanation

Fig. 1 is the signal waveform schematic diagram of multi-pulse trailing edge encoding scheme.

Fig. 2 is the communication process schematic diagram of multi-pulse trailing edge coding system.

Fig. 3 is that conventional LED drives schematic diagram.

Fig. 4 is when the driving signal of LED is high and low level respectively, the flow direction schematic diagram of electric current.

Fig. 5 be communications illuminating system realize device schematic diagram.

Detailed description of the invention

Accompanying drawing being merely cited for property explanation, it is impossible to be interpreted as the restriction to this patent；In order to the present embodiment is more preferably described, some parts of accompanying drawing have omission, zoom in or out, and do not represent the size of actual product；

To those skilled in the art, in accompanying drawing, some known features and explanation thereof may will be understood by omission.With embodiment, technical scheme is described further below in conjunction with the accompanying drawings.

The ultimate principle of the present invention is by using multi-pulse trailing edge encoding scheme, reduces the transition times of the driving voltage of LED, reduces the excessive power drain caused because of LED junction electric capacity.Use variable length symbol width simultaneously, shorten low duration as far as possible, improve the dutycycle of signal, on the premise of ensureing that brightness of illumination is constant, reduce peak point current.

Fig. 1 is the signal waveform schematic diagram of multi-pulse trailing edge encoding scheme, and the curve of top is its coding principle: when each code element starts, and signal rises to high level from low level, and rising edge is as time reference.Encoder is divided into one group every for data to be transmitted n position, according to often organizing the value of data, and the pulse signal of output different in width.If the minimum slot time of pulse is τ, then the Breadth Maximum of pulse is 2ⁿ·τ.Its trailing edge moment is corresponding with the value of data to be transmitted group.Receiving terminal, according to the trailing edge moment of signal, recovers the value of data to be transmitted, it is achieved the transmission of data.

Curve below Fig. 1 is encoding examples, and the value of the 1st group of data to be transmitted is " 0 ", so pulse only takes up the time slot width of 1 unit；The value of the 2nd group of data to be transmitted is " 5 ", so pulse takies the time slot width of 6 units；The value of the 3rd group of data to be transmitted is " 4 ", so pulse takies the time slot width of 5 units.This waveform appears to pulse width modulation conventional in analog power and the combination of pulse frequency modulated scheme, but it is essentially different: pulse width modulation and pulse frequency modulated technology are to represent analogue signal with digital signal, it is that analog signal level is carried out digitally coded method, and the present invention is the value characterizing binary data group by pulse falling edge or pulse width, belong to a kind of multicomponent coding mode.

Its communication process is as shown in Figure 2: data to be transmitted passes through n position consolidation circuit, is divided into the data set of one group, n position.Pattern generator receives data set waiting for transmission, changes into polynary trailing edge coding signal.Such as, the polynary trailing edge coding of n position to be realized, n digit counter can be used to realize: set counting cycle of enumerator as τ, the value of n position data to be transmitted is k, in each cycle, and encoder output high level, unison counter starts counting up, when the count value of enumerator is identical with data to be transmitted value, encoder output low level, and reset count device.So output pulse width of encoder is equal to k τ, then corresponds to the value of data to be transmitted.After encoder output low level, rise with the speed that system is the most possible immediately, carry out the transmission of next code element.The output signal of pattern generator, after analog line driver amplifies, drives LED, produces optic communication signal.

At receiving terminal, optical-electrical converter receives optic communication signal, through the judgement of comparator, recovers polynary trailing edge coding signal, eventually passes decoder decoding, obtain n-bit data group, then recovered data to be transmitted by data recovery circuit.Decoder can also use n digit counter to realize: at each signal rising edge, enumerator starts counting up, and the trailing edge of signal stops counting, and count value, with regard to respective pulses width, can obtain the data to be transmitted value of correspondence.

According to the principle of such scheme, analyze the characteristic in terms of the power consumption and brightness of illumination that this scheme causes at LED junction electric capacity respectively:

1, the energy expenditure that LED junction electric capacity causes

It is that conventional LED drives schematic diagram as shown in Fig. 3 (a), generally uses the driver of a high speed to drive LED.But, owing to the junction capacity of illuminating LED is the biggest, in the magnitude of nF, High-speed driving signals will produce bigger power attenuation to the discharge and recharge of this electric capacity, thus reduces the luminous efficiency of illuminator.The power consumption that junction capacity discharge and recharge causes can be according to Fig. 3 analysis.Fig. 3 (b) is the driving schematic diagram after replacing it with the equivalent circuit of LED, in dotted line frame is wherein the equivalent circuit diagram of LED.Because mainly studying the impact of LED junction electric capacity, so ignoring the factors such as the series resistance of LED, LED is equivalent to a desired illumination diode D and LED junction electric capacity C_LEDParallel connection.

When the driving signal of LED is high and low level respectively, the flow direction of electric current is as shown in Figure 4.Because what the discharge and recharge of electric capacity only occurred in signal rises or falls edge, so being analyzed the situation of signal rising edge and trailing edge separately below:

(1) during signal rising edge, the circuit energy consumption that LED junction electric capacity causes

Fig. 4 (a) is to input the sense of current for during high level, now internal drive switch S Guan Bi, power supply V_HBy driver internal resistance R_OPowering to preferable LED makes it luminous, gives the junction capacity charging of LED simultaneously.

The energy that the charging of LED junction electric capacity is consumed by power supply is not involved in luminescence, is the energy expenditure of circuit.Because electric capacity not consumption of electric power, so actual power all consumes on drive circuit, i.e. in the internal resistance of drive circuit.The energy expenditure driving signal rising edge saltus step to cause the discharge and recharge of junction capacity can use formula (1) to calculate:

$\begin{array}{c}{J}_{rise}={\∫}_0^{t_r}{i}_C\·v_{Ro}dt\\ ={\∫}_0^{t_r}{i}_C\·(V_H-v_{LED})dt\end{array}---\left(1\right)$

In formula, i_CFor flowing through the electric current of LED junction electric capacity, v_RoFor the voltage in driver internal resistance, V_HFor driving the voltage of signal high level, v_LEDFor the voltage (voltage equal on LED junction electric capacity) on LED, t_rFor signal elevating time.

It is equal to for flowing through the electric current of LED junction electric capacity:

$i_C=C_{LED}\frac{{\mathrm{dv}}_{LED}}{dt}---\left(2\right)$

Because when signal keeps high level or low level, the voltage of LED keeps constant, and its junction capacity does not has discharge and recharge, and the junction resistance of LED and the internal resistance of driver constitute simple bleeder circuit, so having:

$v_{LED}=V_H\frac{r_{LED}}{r_{LED}+R_O},V_{in}=V_H---\left(3\right)$

$v_{LED}=V_L\frac{r_{LED}}{r_{LED}+R_O},V_{in}=V_L---\left(4\right)$

R in formula_LEDFor the junction resistance of LED, R_OInternal resistance for driver.Because the internal resistance of LED is much larger than the internal resistance of driver, so before rising edge, the voltage on LED approximates low level V_L, the voltage after rising edge approximates V_H, formula (2), (3) and (4) is substituted into formula (1) can obtain:

$\begin{array}{c}{J}_{rise}={\∫}_{V_L}^{V_H}v\·C_{LED}dv\\ =\frac{1}{2}{C}_{LED}{(V_H-V_L)}^2\\ =\frac{1}{2}{C}_{LED}{V_m}^2\end{array}---\left(5\right)$

V in formula_mDifference for low and high level.From formula (5), during signal rising edge, the circuit energy consumption that junction capacity causes is directly proportional to the size of junction capacity, to square being directly proportional of the peak-to-peak value driving signal.

(2) during signal trailing edge, the circuit energy consumption that LED junction electric capacity causes

Fig. 4 (b) is when input voltage is low level, the sense of current of each several part.Now internal drive switch S Guan Bi, the electric charge that LED junction electric capacity accumulates when high level is discharged by the internal resistance of driver, and is discharged by preferable LED simultaneously, and discharge current is gradually reduced, and LED gradually extinguishes.So having:

$\begin{array}{c}{i}_C=i_{Ro}+i_D\\ =C_{LED}\frac{{\mathrm{dv}}_{LED}}{dt}\\ =\frac{v_{LED}-v_L}{R_O}+i_D\end{array}---\left(6\right)$

The energy of the internal resistance flowing through driver is useless, so the circuit energy consumption that junction capacity causes is:

$\begin{array}{c}{J}_{fall}={\∫}_0^{t_f}{i}_{Ro}\·v_{Ro}dt\\ ={\∫}_0^{t_f}(i_C-i_D)\·(v_{LED}-V_L)dt\end{array}---\left(7\right)$

I in formula_DFor flowing through the electric current of desired illumination diode, the equation that the forward C-V characteristic of preferable LED is followed is:

$i_D=I_0\[\exp \left(\frac{{\mathrm{qv}}_D}{nkT}\right)-1\]---\left(8\right)$

In formula, I₀For the reverse saturation current of LED, q is electronic charge, v_DFor LED both end voltage, n is constant relevant with the material of LED, between 1 to 2, and k is Boltzmann constant, and T is absolute temperature.

Formula (6) and formula (8) are substituted into formula (7), and when can obtain signal trailing edge, the energy expenditure that the junction capacity of LED causes is:

$\begin{array}{c}{J}_{fall}={\∫}_{V_H}^{V_L}{C}_{LED}(v_{LED}-V_L){\mathrm{dv}}_{LED}-{\∫}_{V_H}^{V_L}{C}_{LED}\frac{I_0\[\exp \left(\frac{{\mathrm{qv}}_D}{nkT}\right)-1\](v_{LED}-V_L)}{I_0\[\exp \left(\frac{{\mathrm{qv}}_D}{nkT}\right)-1\]+i_{Ro}}{\mathrm{dv}}_{LED}\\ ={\∫}_{V_H}^{V_L}{C}_{LED}(v_{LED}-V_L){\mathrm{dv}}_{LED}-{\∫}_{V_H}^{V_L}{C}_{LED}\frac{R_O{I}_0\[\exp \left(\frac{{\mathrm{qv}}_D}{nkT}\right)-1\](v_{LED}-V_L)}{R_O{I}_0\[\exp \left(\frac{{\mathrm{qv}}_D}{nkT}\right)-1\]+v_{LED}-v_L}{\mathrm{dv}}_{LED}\\ =\frac{1}{2}{C}_{LED}{V_m}^2-{\∫}_{V_H}^{V_L}{C}_{LED}\frac{R_O{I}_0\[\exp \left(\frac{{\mathrm{qv}}_D}{nkT}\right)-1\](v_{LED}-V_L)}{R_O{I}_0\[\exp \left(\frac{{\mathrm{qv}}_D}{nkT}\right)-1\]+v_{LED}-v_L}{\mathrm{dv}}_{LED}\end{array}---\left(9\right)$

In formula, Section 1 is the energy stored on LED junction electric capacity, and Section 2 is the energy that LED consumes during trailing edge, although signal of communication is not contributed by this portion of energy, but for luminescence.Because the internal resistance of LED is much larger than the internal resistance of driver, so during signal trailing edge, the energy that the energy that driver internal resistance consumes consumes much larger than LED, the energy dissipation that LED junction electric capacity causes approximates:

$J_{fall}=\frac{1}{2}{C}_{LED}{V_m}^2=J_{rise}---\left(10\right)$

(3) during signal saltus step, the circuit power consumption that LED junction electric capacity causes

The circuit power consumption that LED junction electric capacity causes is equal to the energy expenditure of saltus step every time in the unit interval.Therefore, the probability factor to each cycle saltus step is α, and signal frequency is the driving signal of f, and according to formula (5) and (10), the power consumption that the discharge and recharge of junction capacity causes is:

$P=\mathrm{\α}\·f\·J_{fall}=\frac{1}{2}\mathrm{\α}\·f\·C_{LED}\·{V_m}^2---\left(11\right)$

As a example by the LED of common power 1W, its typical junction capacity 1nF, if driving voltage switching frequency 100MHz, modulation voltage 3V, (to unipolarity nonreturn to zero code α=0.5 during employing unipolarity nonreturn to zero code, other pattern α can be much higher), its power consumption has reached 150mW, and this will cause the very big reduction of luminous efficiency.If frequency promotes further, or junction capacity increases (situation of great power LED), and this problem will be more serious.

(4) method reducing the circuit power consumption that LED junction electric capacity causes

According to formula (11), the circuit power consumption that LED junction electric capacity to be reduced causes, clock frequency can be reduced by reducing the probability driving signal saltus step, reduce LED junction electric capacity, reduce the methods such as drive signal amplitude and realize.Because once LED selectes, its junction capacity size determines the most substantially, in order to obtain sufficiently high signal to noise ratio, drive signal amplitude also must be sufficiently high, so most viable method is through improving coding or the modulation system of communication system, reduce the probability driving signal saltus step, and reduce clock frequency.

The multi-pulse trailing edge encoding scheme that the present invention uses can effectively reduce probability and the clock frequency driving signal saltus step: as a example by using n position m primitive encoding, system transmitting terminal uses the rising edge of driving pulse as timing reference, data according to required transmission, use m primitive encoding, the corresponding different pulse falling edge position of each code value, after driving pulse declines, rise with the speed that system is the most possible immediately, carry out the transmission of next code element.

It can be seen that in a symbol time, signal saltus step twice, transmit n bit, the probability factor of each of which cycle saltus step is α=2, and its signal frequency isTherefore the power consumption that its junction capacity discharge and recharge causes is:

$P=\frac{2}{n}\mathrm{\α}\·f\·C_{LED}\·{V_m}^2---\left(12\right)$

Therefore the power consumption that LED junction electric capacity causes compares basic unipolarity nonreturn to zero code signal, has been reduced to originalWhen n is sufficiently large, can greatly reduce the excessive power drain problem that LED junction electric capacity causes.

2, the brightness of illumination problem that pulsed drive causes

As it was previously stated, employing pulse drive signal, if to take into account the luminescent lifetime of brightness of illumination, luminous efficiency and LED simultaneously, best bet is exactly the dutycycle improving signal.

When considering the dutycycle of signal, if the low level width of minimum is t_L, the slot time of trailing edge difference code value is t_cThen, for n position m primitive encoding, average symbol width isAverage dutycycle is

$D=\frac{(m+1)\·t_c}{(m+1)\·t_c+2t_L}$

When m is sufficiently large when, dutycycle levels off to 1.Visible the solution of the present invention can also improve the dutycycle of LED drive signal.

Be as shown in Figure 5 a kind of LED-based high illumination efficiency visible light communication illuminator realize device, transmitting terminal mainly comprises the n position that is made up of FPGA and merges encoder and pattern generator, analog line driver and LED.Receiving terminal mainly comprises decoder and the data recovery circuit that photo-detector, comparator and FPGA are constituted.Described n position consolidation circuit and pattern generator receive data to be transmitted, are converted to polynary trailing edge coding signal, and this signal after driver is amplified, drives LED, produces optic communication signal.At receiving terminal, optical-electrical converter receives optic communication signal, through the examination of comparator, recovers polynary trailing edge coding signal, eventually passes the decoder decoding that FPGA is constituted, recover signal to be transmitted.

Above-mentioned FPGA uses the EP2C5 chip of altera corp cyclone-II series, logical block 4068, dynamic memory total bit number 119808bit on sheet, embedded 18x18 multiplier 13, phaselocked loop 2 on sheet.

Above-mentioned analog line driver uses the ZHL-6A amplifier of mimi-circuit company, passband 0.0025-500MHz, gain 25dB, peak power output 22dBm.

Above-mentioned LED uses the LE_CW_E2B light emitting diode of OSRAM company, rated current 700mA, luminous flux 240-610lm.

Above-mentioned photo-detector uses 1601 optical-electrical converters of new port company, its spectral response range 320-1000nm, bandwidth 1GHz, rise time 400ps, equivalent input noise power 31pW, conversion gain 360/W.

Above-mentioned discriminator uses the max961 comparator of Maxim, its propagation delay 4.5ns, supply voltage 3-5V, output level compatibility TTL and CMOS standard.

Obviously, the above embodiment of the present invention is only for clearly demonstrating example of the present invention, and is not the restriction to embodiments of the present invention.For those of ordinary skill in the field, can also make other changes in different forms on the basis of the above description.Here without also cannot all of embodiment be given exhaustive.All any amendment, equivalent and improvement etc. made within the spirit and principles in the present invention, within should be included in the protection domain of the claims in the present invention.

Claims (4)

1. the implementation method of a communication illumination sharing system based on LED high illumination efficiency, it is characterised in that

At transmitting terminal, data to be transmitted is merged encoder by n position and is divided into the data set of one group, n position, pattern Data set is converted into polynary trailing edge coding signal by generator, and polynary trailing edge coding signal is through power drive After device amplifies, LED emission is driven to produce optic communication signal；

At receiving terminal, optical-electrical converter receives optic communication signal, through the judgement of comparator, recover polynary under Fall is along coding signal, then decodes through decoder, obtains n-bit data group, then is recovered by data recovery circuit Data to be transmitted.

Implementation method the most according to claim 1, it is characterised in that at transmitting terminal, every secondary data passes During defeated beginning, data to be transmitted signal rises to high level from low level, and rising edge is as time reference, n Position merging encoder is divided into one group every for signal to be transmitted n position, according to often organizing the value of data, and output different in width Pulse signal, the pulse signal trailing edge moment is corresponding with the value of data to be transmitted: set between the minimum time slot of pulse Being divided into τ, the value of n-bit data is x, then the width of pulse is (x+1) τ.

Implementation method the most according to claim 1, it is characterised in that it is low that n position merges encoder output After level, rise immediately, carry out the transmission of next code element, so the length of each code element is change.

4. one kind based on LED high illumination efficiency communication illumination sharing system realize device, it is characterised in that Including n position merge encoder, pattern generator, analog line driver, LED, optical-electrical converter, comparator, Decoder and data recovery circuit, merge encoder by data to be transmitted by n position and be divided into the data of one group, n position Group, data set is converted into polynary trailing edge coding signal by pattern generator, and polynary trailing edge coding signal passes through After analog line driver amplifies, LED emission is driven to produce optic communication signal；Optical-electrical converter receives optic communication letter Number, through the judgement of comparator, recover polynary trailing edge coding signal, then decode through decoder, obtain N-bit data group, then recovered data to be transmitted by data recovery circuit.