JPS6037792A - System for stabilizing photo output - Google Patents

Abstract

PURPOSE:To stabilize the photo output by a method wherein part of the photo output from a semiconductor light emitting element is detected and so controlled as to decrease at a larger constant than that for reducing the photo output when the result is larger than the first or second reference signal, and at a smaller time constant than that for decreasing the external temperature. CONSTITUTION:The outputs from a driving part 2 having a data input terminal 1 and a bias impressed part 4 having a transmission demanding signal input terminal 3 are supplied to a semiconductor light emitting element 5. A semiconductor photo detector 6 detects part of the photo output from the element 5, which output is then supplied to the impressed part 4 via comparator 8. The signal corresponding to the threshold value of the element 5 is supplied from a reference signal input terminal 7 to the comparator 8, and this signal is switched over to the corresponding signal in the case where the thermal sag phenomenon of the element 5 does not generate at the same time with the input of a burst data signal to the element 5. Further, the impressed part 4 is provided with a discharge functional element 16 in such a manner that the output decreases, in the case of stopping the increase in the bias current of the element 5, at a larger time constant than that for reducing the output and at a smaller constant than that for decreasing the external environmental temperature. Thus, the photo output can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technology of the invention 'y'f field] The present invention relates to a light output stabilization method, and 'l! Part I relates to a method for stabilizing the optical output of a single-layer monolithic light emitting device in an optical network.

[Conventional technology and its problems] Improving work efficiency is important for improving society's productivity. Divide or disperse the relatively expensive fz')-space of the so-called Ailservers who are responsible for such consolidation.
In order to realize a network system that is inexpensive for use, reports have been made on the development of bus-type or star-type networks.

How many months are handled on such a network, for example], OP
A high value of 2 or higher is 1 (normally, this is a so-called burst signal in which data is transmitted only for a certain period of time).

However, in such optical transmission technology, problems that did not occur in the optical transmission technology using the same 1 Qil cable have arisen, especially when dealing with burst signals.

This is obvious from the fact that the luminous efficiency of a semiconductor light emitting element, such as a semiconductor laser (hereinafter abbreviated as LD), is very sensitive to temperature.

That is, the semi-quartet light-emitting element absorbs the light heat of the semiconductor photodetector's own moon and the 7.7 degrees of the evening environment during burst signal transmission. ~1, ftj: Ura Nika no Kage g Money Receiver 'C1 Example V1゛1・J] In L I
) Due to the heat generated by the element itself, the threshold is 11' and 1υ1'L.
, and this causes the output to drop and parse) (
l, +-j;, x = t, "kizab wedge", the threshold current changes due to the generation of dust, the aging of the 11ζ external environment 1'119F1, and the output decreases to 2 qh-J. Ru.

As a method to suppress the instability of the light output of such a half-body light-emitting element, the pH of a half-body light-emitting element has a strange increase (i, J,;
So-called analog control has been developed.

However, in order to achieve such a response of 2,000% IHz or more, a high-speed circuit element of 1J value is required, and Cow?! The engineering body >'r, ;<・Child drive vehicle v] C's bar'';'The two effects of addition and O-decrease are busy/The light detection element and transistor in the eyebrow circuit, etc. ;Ii;i There was a problem in that oscillation caused by 9p- occurred and the circuit itself became unstable.

Therefore, such semiconductor light emitting 2.
As a way to suppress bones, the applicant! 14 Gansho 5B-
I applied for No. 30779.
-3 (No. 1779) is for stabilizing and controlling the burst light output of a semiconductor light emitting element. That is, a part of the burst light output of the semiconductor light emitting element is optically detected by a semiconductor photodetecting element,
This photodetection signal is compared with the first or 28th reference signal, and if the photodetection signal rr +,j is smaller than the first or second reference signal, the bias signal of the semiconductor light emitting element is This is a burst light output stabilization drive system in which the bias (Fi) is maintained at a constant value when the light detection signal becomes larger than the first or second reference signal. In the output stabilization driving method, sufficient output stabilization is achieved during the burst period only by forcibly increasing the bias of the semiconductor light emitting element.

This is because the burst period is usually several ms, and within this period, even if the 171'LD is not affected by temperature changes in the external environment, η is generated by the heat generated by the semiconductor light emitting element itself.
1 tone output low to 8 1, lead to only elephant being dominant.
2. It's on.

(If the transmitted signal is not a burst signal of several ms in M', but a longer burst signal or a general continuous signal, the half-2, C1-body emitting Yonago is If only the heat generated by the body light-emitting element itself is generated, then the temperature change in the surrounding area is also taken into account.There is a circle.
The temperature of the external environment is rising and the cliff 2. Yui 1, when the threshold current of the luminescent female increases) Jl, q! l le + j 1977-30
774J-February 2010 By this method, it is possible to achieve C, which aims to make the light output more affordable.

However, when the temperature of the external environment decreases, that is, when the threshold current of the semiconductor light (I) element decreases as the external temperature decreases, the firewood must be replaced by 1 j of firewood until the EJ level that controls this decreases. not present.

Therefore, not only the influence of the heat generated by the element itself, but also the influence of the temperature of the external environment.
ill (l'tllt.

I wanted a way to get it.

[Object of the invention] The present invention has been made based on the points of the above F7JΣ.
5, y, 471) due to the heat generated by the semiconductor light emitting element itself and /11 part J: Eliminate the influence of 1 degree change in the HH boundary 2
, /2 - compatible with the strike signal and the number of consecutive months in general 1
The purpose of this invention is to provide a C1 output stabilization method that stabilizes the feedback loop to accommodate this problem.

[Existing Summary of the Invention] Part of the light output of the semiconductor light emitting device is photodetected by a semiconductor photodetection device, this photodetection signal is compared with the first or second forward signal, and the photodetection signal is determined to be the first or second signal. When the second reference signal is smaller than the first or second reference signal, increase the bias signal of the semiconductor light emitting element, and when the light detection (Fffi number is larger than the first or second reference signal), increase the number of 7477411. Obtain an optical output stabilization method in which the bias beam level is decreased to a time constant that is larger than the time constant for optical output reduction and smaller than the time constant for temperature change in the external environment after the bias signal is stopped. That's how it is.

[Effects of the Invention] According to the present invention, the photodetection of the semiconductor photodetection element and the first
~〈 is a digital output by comparing with the second reference No. 18, and by performing control to increase or stop increasing the bias of the single-layer 8-body light emitting element with the digital output of 4+V, return The stability of the loop is improved, and the function n1 of the stabilizing control loop is also made very easy.

Furthermore, regarding the bias of the half-2R body light emitting element, the circuit configuration is easy because it is sufficient to simply increase the bias signal.

Furthermore, by keeping the bias signal level low at a time constant that is larger than the time constant of the light output reduction of the semiconductor light emitting device and smaller than the time constant of the temperature change in the first part of the evening environment, especially during the burst 1lJI. ms): Parse inside)
(It is not limited to 8 issues, but can also be applied to bursts with longer burst periods (, J issue, or general continuous 17 issue 2).

That is, it is possible to obtain an inexpensive and stable optical output stabilization method.

[Examples of fruitful inventions]

Below are examples of ff1Q by Kazumi Ki and Kumei in Figures 1 to 41.
See ゛'＜1! (I will explain the explanation below.

FIG. 1 shows the 11jν diagram of the circuit used in this embodiment.
16: A pulse 1 drive unit (2) with a transmission general request input store 61 (3) and a bias application unit (4) that completely cures are provided, and this pulse drive unit (2) and a transmission safety A bias applying section (4) is provided to apply the signal input terminal (3), and the pulse driving section (2) and the bias applying section (4)
) is input, for example, L D
A semiconductor light emitting device (5) consisting of the following is provided.

In addition, a semiconductor photodetector element (hereinafter abbreviated as PD) (6) consisting of, for example, a circular N photodiode, which detects a part of the optical output of this LD (5), and a semiconductor photodetector element (hereinafter abbreviated as PD) (6), which detects a part of the optical output of this LD (5), and this FD (refer to the output of (3)) A comparator (8) is provided to compare the signal input from the signal input terminal (force).

The output of this comparator (8) is input to a bias application section (4) to control the output of the bias application section (4).

Next, the operation according to the present invention is shown using a time chart of the No. 411 waveform and the output waveform of the LD (5) during the operation (2) in the circuit configuration described above.

In this case, the data signal shown in FIG. 2 is a burst signal, and the burst period is several ms at most, which means that the influence of temperature changes in the external environment is 1. shall not be accepted.

First, burst data input (Fig. 2 (a)) is inputted to the pulse and drive unit (2) from the burst take input node 4 (1). Request signal to be sent in advance
From there, the bias applying section (4) is sent to the bias applying section (4).
2'412 (1)) ) is input.

The bias application section (4) is connected to the
+))) and the comparator (8) output is input. The comparator (8) compares the photodetection signal of the PD ((3) with the first or second light 8t1 Kure signal, and then outputs a low signal when the photodetection signal No. 15 is smaller than the reference (Fi signal), and a high signal. When it becomes I
(Performs igb output.

The bias application unit (4) receives a sending request signal (Fig. 2 (+3
)) and operates only when receiving the low output of the comparator (8), ], J) (5) is biased.

Normally, before the burst data is input manually (Figure 2 (a)), strictly speaking, before the transmission request signal (Figure 2 (1, 1)) is input, 1 no I) (5) does not emit light. Therefore, light 4θ1
The number 1 is the first number corresponding to the threshold value of L L) (5).
The reference number 1-1 becomes small, and the output of the comparator (8) becomes Low.

Therefore, the bias applying section (4) transmits the transmission absorption signal (second
Figure (+))) works for the first time when it is manually operated, and L
I) The bias in (5) is applied to the bias applying unit (4) with the transmission request number (2P 2 lbi?+ (+))) and O
- Continues as long as the Low /j small output of the comparator (8) is input. After that, the torch of applied bias causes L J
) The bias light of (5) also increases, and the light detection light of (6) (PI) (6) becomes thicker, I-, D (
5), the outputs of the comparator (8) are ILi and LIigl+.

Accordingly, the bias applying section (4) sends a request to send 1.a.
Even if the comparator (8) is operated manually, the output of the comparator (8) is IJigh, so it does not operate and there is no increase in the bias of the LD (5). From this ζ, L I) (5) is biased to the threshold value. At this bias, the photodetection of I・1)(6)・11
When No. 1 becomes smaller than the first reference signal, the comparator (8
) becomes Low and bias application section (4) 75th printing F
(5) Keep the bias at the threshold.

In this way ■・I) (5) 1・11. The input of the transmission request signal ((+) in FIG. 2) is biased to the threshold value J. After that, there is data (aj12 (a))
is input to the LD (5) via the pulse and drive section (4),
LD(5) emits light in response to the burst detector II 4'J (FIG. 2(a)). The burst data signal is as shown in Fig. 2(a).
It is a high-speed burst bow of about 11z.

9 pj-, which is input to the comparator (8), Shinzuki is
Ll) (5) burst data No. 15 (jQ Figure 2 (a
) At the same time as human power? br from the reference signal of P,■
2's gradient += A: Switch to < sign. This second impeachment'
fM is a burst data signal (L in Fig. 2(a)).
I) This is a signal corresponding to the optical output when the thermal subcolor development in (5) does not occur. L I) (5) emits light in response to the burst data signal (Fig. 2 (a)), but due to the ":, t" appearance of L and D (5), 1.
, the light output of (5) decreases.

The burst data signal (I in Figure 432) is superimposed on the bias signal from the bias applying section (4) and
J) Input in (5). However, this match,
As the optical output of I, j) (5) decreases, 111) (6
) of 9'(, detection; jj (IIc) decreases and therefore becomes smaller than the second %lji signal 3, and the output of the comparator (8) becomes 1NOOW.

The bias applying section (4) operates in the slave one, and LL' (
5) is biased, and the optical output of JJ D (5) is L
Ill (5) is rain-proofed from decreasing due to the heat sink phenomenon.

It should be noted that the transmission number I, -1 (C112, (b)) is transmitted just as the transmission of the burst period (71%, Fig. 2 (a)) is about to end.

In the above case, the number of increases between burst Jt'1 is Ill S
At the time of burst light output, only 2 cares occur due to the temperature due to its own heat generation, and L I) (5)
) has a tendency to decrease.

By means of a control loop consisting of I) D (6), comparator (8), and bias application section (4),
The optical output of 5) corresponds extremely accurately to the burst data signal (FIG. 2(a)), as shown in FIG. 2(C).

Crossover 1 data type 1. V or Perstoy; 4J,
The burst period of L is relatively longer than that of upper horn E,
1・I when receiving the influence of temperature change in the external environment 7i + ψ
)(5) The stabilizing force θmi of the optical output is shown in Fig. 3(a) to (
(The situation will be clarified with reference to Figure 31 (8) to (d).
is the change in the external environmental humidity when the external ambient temperature drops during the burst data signal transmission (tz to t2) during the burst period of the burst data signal.
I) f in (5); indicates low output ν2, etc.

Figure 3 (a) shows the 1. Represents the agglomeration of external environmental temperature for a period. Let the time constant of the temperature change curve of this evening's environment be 'r. Figure 3 (
b) shows the optical output reduction of (5) when the increase in the bias signal level is stopped and the t is 12 periods, and the time constant of this optical output reduction is 1゛2. do.

This is done after the bias signal level has stopped increasing.
This represents the time constant for reducing the optical output when the optical output stabilization control shown in (5) is not performed as shown in the figure.

Next, FIG. 3(C) shows the control of the bias level 1)-ke according to the present invention. That is, when the increase in the bias signal is stopped, this bias I1i level becomes
T, 1. ) (5) Light output reduction (Figure 3(b))
, the time constant T of the temperature drop in the external environment (Figure 2b3 (a)) is 11
! 11. ,, z 7A should be done a little. This makes the time constant of the 747748 month level reduction ゛1゛, L
I) Time constant 'P of optical output reduction in (5) (Fig. 3 (h))
By increasing T3 to a value larger than 2, the burst light is prevented from rapidly decreasing and the light output of LD (51) becomes unstable.Furthermore, T3 is set to By making the time constant T of !'J (a)) smaller than the time constant T of L I) (5), it is always sufficient to stabilize the optical output in one direction, that is, by increasing the bias No. 411. Therefore, even if the transmitted signal consisting of berth I-(U) is affected by thermal changes in the external environment, Ll)(5
) can be stabilized as shown in the third section 1(d) (t and t are constant and constant).

Furthermore, the operation of the bias application section (4) will be explained next with reference to a circuit diagram showing an example of the bias application section (4) shown in FIG.

The bias application section (4) is provided with a constant current source switch consisting of a constant -11 current source (10), a first transistor (1υ), and a 2nd transistor (1).

When the output of the transistor (8) is Low, the transistor (11) of A is OFF, and the second transistor (12) is OFF.
turns on and charges the capacitor 04).

In addition, when the output of the comparator (8) is Ilight, the J-th transistor θ1) is a transistor with 0NXQ'<2 (
+21 is turned off, and capacitor 04) is not charged.

That is, when the output of the comparator (8) is Low, the capacitor Oa is charged, and the j2 column 7 of this capacitor Oa)
The ji pressure increases the bias increasing function of the LD ((!,) and increases the optical output.

If the output of the comparator (8) is Ilight J, ``), stop charging the capacitor (14), ■, D (5
Stops the increase in + bias current. Therefore, if the burst period of the burst signal is at most several IllS, the fifth Igl (a
) (Comparison as shown in Figure 1 (information waveform diagram during operation of ψ): R knee 1 (8) output causes capacitor (
1 (1), the terminal output of the capacitor 00 is not shown in FIG. 5 (11), and the L sea urchin ratio Mil! Vessel (8
) Output Lo%V level (-< is set to Ilight level, then charge or hold #Y: Repeat.)
He began to continue his second promotion.

Furthermore, if the burst period of No. 5 is long enough to be affected by temperature changes in the external environment, the LD
When the increase in the bias current in (5) is stopped, the optical output decreases at the bias exhaustion level I, D (5) (Figure 3 (b))
is larger than the time constant T2, and the temperature drop in the external environment (
The discharge function element Q6) is provided so that the discharge function decreases with a time constant T3 smaller than the time constant T1 in FIG. 3(a).

This discharge machine M'j Saiko (1, [i) is designed to follow changes in the external environmental temperature while ensuring system stability, and its discharge time constant is determined by the output of LD (5). It is set to be larger than the reduction time constant and smaller than the time constant of threshold current change due to temperature change in the external environment. With this discharge 1 function and bias increase function, even if the external temperature drops by 9 J$, ♂1 degree, the bias level will drop before that and will continue to increase and always stay at the proper position.

This Tj! The I-electric power element 06) is here constituted by a resistor, and assuming that there is no other current leakage, its discharge time constant is as follows: As mentioned above, since it is set to follow changes in the external environmental temperature, the value is usually several seconds or more, and does not become an obstacle when increasing the bias.

Further, this discharge function is not limited to a resistor, but may be a pace current or the like injected into the transistor 07 that drives the LD (5).

Furthermore, this discharge time constant should not only be set in response to changes in environmental temperature, but also in other cases where the output changes due to installation, the g7 has a configurable discharge function that follows the required rate. It's fine if you have it.

In addition, the discharge of the capacitor 04) between bursts can be achieved by turning on the switch (15) that turns on the data signal +3 (Fig. 2 (, +)).
l, 1, good.

In addition, in the above, we have explained the case of a semiconductor generator, Ajiko is half 2, and a laser (LI)) 5, but this is
It is clear that the present invention is applicable even to the case of one diode (T, ED).

[Brief explanation of drawings]

FIG. 1 shows a circuit used in an embodiment 611 of the present invention ((Y component, FIG. 2(a) to (C), FIG. 5(a) to (b)
Figure 3 is a time chart showing the Buddha waveform and 0 output waveform during the operation of each part of the -1, 1st to 1st circuit diagram. , i31
, 4 times, FIG. 4 is a circuit diagram showing an example of the bias application section shown in FIG. 1. 1...Data input terminal 72...Pulse, drive section 3...
・1t'4 (N"Ikui 1; Gojinki Vlfijko 4・
・Bias application unit 5 ・Half-quad light emitting element 6 ・・t
'-Conductor light detection element 7...Reference signal human power 14;
8..., Comparator 10... Dingtun flow source 1], 12...
・l・Lanzisk 13・Logic gate 14・Capacitor 15-...Switch 16...Resistor 17...j+'-body emission (-, ≧ Child drive transistor 18''' tjim L211 game l Ili + 11 people Patent attorney Ken Nori Chika 14.i (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (6)

[Claims] (1) Optical output of the semiconductor light emitting device -f~b=-+'q
A light output stabilization method for stabilizing and controlling the power of the light detection element and the light detection signal.
11) I'1) -Cz Compare the light detection believer with the first or second reference j1 request! The first photodetection signal is
Wakaf F ma appetizer) Part 1 of 2! d 'If the number is small, please add the above half'), add 19 'Irome Uko No. When compared to the second reference signal (for physical education), after stopping the increase in the number of yashii iris, the increase in the number of yashii iris is increased, and then the level of the iris is adjusted to the level of the light Yoi Tower (Yoi)
) is also large, the force is large, and the external ring'(, 5's fortune 1L ([The fact that it is smaller than the time constant of descent and decreases by the number of 1 hour is 'l'j sign) jf; ltl force stabilization force (2) 1st 6 yen (f'j A&J', %h-approximately with respect to the threshold value of the semiconductor light emitting device (!-4r\F Claim 1tii 1st JJ' 4 1
1. Grass light output stabilization method. (3) The second reference signal corresponds to the signal input to the semiconductor light emitting device for outputting light. □l: Optical output stabilization method. (4) The semiconductor light emitting device is characterized in that, when a signal is input to the semiconductor light emitting device for outputting light, the bias signal is inputted prior to the input of the signal. q; ] χ Box 213] ``Light output stabilization method. (5) When inputting a signal to the semiconductor light emitting device for adjusting the light output, the reference signal is inputted from the first reference signal to the second reference signal.
The rare g'r ii whose 4'Y characteristic is to be the reference signal for
Range of i': °C8 output stabilization method described in item 1. (6) The light output of the semiconductor light emitting device is burst ``r, output 4''! 4゛ν permission request 1.]
1 circle>4'71 Optical output stabilization method described in J'j1.