JPH03280024A - Optical pulse signal delay device - Google Patents

Abstract

PURPOSE:To delay an optical pulse signal by a set time and to compensate the loss of an optical signal by providing an optical switch which can switch the optical path between an input and an output terminal, an optical fiber for delay, an optical amplifying element which is interposed halfway, and a timing control part which sets a delay time. CONSTITUTION:The delay device is equipped with the optical switch 23 which can switch the optical path between the input and output terminals, the optical fiber 36 for delay which is coupled between the input and output terminals, the optical amplifying element 32 which is interposed halfway, and the timing control part 26 which sets the delay time by outputting the switching control signal for the optical switch 23. Namely, the input optical pulse signal passes through the delay fiber 36 and returns to the other light input terminal. Namely, when the optical path is switched again right before the light returns, optical pulses are confined to the delay fiber and in the case of the lapse by the number of times of confinment set by a timing control part 26, the optical pulses are outputted from the light output terminal. The loss of light in the period is compensated by an optical amplifying element 32. Consequently, an optional delay time can be set by the simple constitution and the device which is free from the loss of the optical signal at the time of delay is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical pulse signal delay device that delays an optical pulse signal by a set time and compensates for loss of the optical signal.

"Prior Art" Conventionally, an apparatus as shown in FIG. 6 or 7 has been used to measure an optical pulse signal waveform. In the figure, thin solid lines represent optical signals, and thick solid lines represent electrical signal paths. In these devices.

A part of the input optical pulse signal is separated by a coupler (1), one part remains as an optical pulse signal, and the other part is converted into an electric pulse signal for triggering and inputted into the optical pulse measurement quantity (4). Of these, the other optical pulse signal is sent to the light receiving element (2).
The signal is converted into an electric pulse signal by the trigger circuit (3), and further waveform-shaped and amplified by the trigger circuit (3), and then input to the optical pulse measuring device (4) as a trigger electric pulse signal. At this time, the light receiving element (
2) and the trigger circuit (3), a signal delay occurs. In order to compensate for this delay time, conventionally, a part of the optical pulse signal separated by the coupler (1) is introduced into an optical fiber (5) as an optical delay path, as shown in FIG. The input timing to the optical pulse measuring device (4) was adjusted by varying the length of the optical fiber (5).

Further, as shown in FIG. 7, a part of the optical pulse signal on one side of the beam splitter (1a) is transmitted through a prism (
6) and was adjusted by varying the position of this prism (6).

Furthermore, there were also devices that used both FIGS. 6 and 7.

Note that fine adjustments were sometimes made using electrical delays.

Additionally, there were delay devices for continuous optical signals as shown in Figures 8 to 10 (Japanese Unexamined Patent Publication No. 53-203
48), which connects a plurality of optical β elements (7) in series, as shown in FIG.
) is the shortest optical line (8) and a sufficiently long optical delay line (9)
Combine with. Here, (10) is an input terminal, (11)
is an output terminal, (12) is a light absorber, and (13) is a control terminal.

As shown in FIG. 9, the optical β element (7) has two input terminals (a) (b) and two output terminals (c) (d).
), the two states of a-+C, b-4d shown in (a) and a-+d, b-+c shown in (b) are determined by the control signal applied to the control terminal (13). can be switched to Specifically, it consists of a voltage-controlled optical directional coupler as shown in Figure 10, with two optical guide lines (15) (16) having the same optical characteristics on an electro-optic crystal substrate (14).
are formed and close to each other in the middle to form a coupling region, and a control electrode (17) is arranged in the center of this coupling region, and electrodes (18) and (19) are arranged on the outside of the plane. With such a configuration, by switching the predetermined optical β elements (7)..., the shortest optical path (8) and the sufficiently long optical delay line (9) are created.
In combination with this, the desired delay time can be obtained.

[Problems to be Solved by the Invention] As shown in FIG. 6, in the case where an optical fiber or mirror is used as an optical delay path, the delay time is fixed by the length of the optical fiber, and the apparatus becomes large-scale.

As shown in Fig. 7, in the case of using a prism, the delay time depends on the distance the prism moves, so it is not possible to obtain a delay time longer than a predetermined value.This is because there is no device that can increase the movement distance. Another reason is that it is difficult to travel long distances without changing the intensity distribution or shape of light.

The device shown in FIG. 8 requires a larger device and is extremely unsuitable for use with optical pulse signals.

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to set an arbitrary delay time to an optical pulse signal with a simple configuration, and to obtain an optical pulse signal without loss of the optical signal during the delay.

"Means for Solving the Problems" The present invention provides an optical switch having at least two optical input terminals and at least two optical output terminals and capable of switching the optical path between these input and output terminals, and at least one of the optical switches.
a delay optical fiber coupled between two input/output terminals, an optical amplification element inserted in the middle of this delay optical fiber,
and a timing control section that outputs a switching control signal for the optical switch and sets a delay time.

"Operation" If the optical path is switched just before an optical pulse signal is input to one optical input/output terminal of an optical waveguide type optical switch, the input optical pulse signal will pass through the delay fiber and go to the other optical input terminal. return. Immediately before this return, the optical path is switched again. The optical pulse is then confined within the delay fiber while the optical path is being switched. While confined, light loss occurs at the input and output parts of optical switches, during transmission through optical fibers, at coupling parts between optical fibers and other elements, and at condensing lenses, but this is compensated for by optical amplification elements.

When the number of times of confinement (delay time) set by the timing control section has elapsed, the optical pulse is output from the optical output terminal with a predetermined delay time.

"Example" An embodiment of the present invention will be described below with reference to FIG.

(20) is an input terminal for the optical pulse signal to be measured, and this input terminal (20) is coupled to a coupler (21) that divides the optical pulse signal into two. This coupler (21)
An optical waveguide type optical switch (
23) are combined. A light receiving element (24) for converting an optical pulse signal into an electrical signal, an amplifier (25), and a timing control section (26) are coupled to the other output, the optical waveguide type optical switch operation signal side.

One output side of this timing control section (26) is coupled to the optical waveguide type optical switch (23) via a waveguide drive pulse timing signal generator (27) and a waveguide drive pulse generator (28). ing. The other output side of the timing control section (26) is connected to the optical delay path (31) for optical amplification through an optical amplification element driving pulse timing generator (29) and an optical amplification element driving pulse generator (30). element(
32). Note that (38) is an optical signal output terminal. The optical waveguide type optical switch (23)
As shown in the figure, it has two optical input terminals (a) and (b) and two optical output terminals (c) and (d), and two waveguides (33) (33) intersect at the center. , this intersection (3
4), parallel electrodes (35) (35) are arranged. In addition, the other optical input terminal (b) and one optical output terminal (
C) A delay optical fiber (36a), a condenser lens (37a), an optical amplification element (32), a condenser lens (37b)
) and a delay optical fiber (36b) are connected in a loop to form an optical delay path (31). The optical amplification element (32) used in this optical delay path (31) is as follows.

A device that can amplify input light with a degree of amplification that depends on an external electrical signal and output it as light.For example, an anti-reflection coating is applied to both end faces of a semiconductor laser to suppress reflections on both end faces. A non-resonant traveling wave optical amplifier (Trave
ling-111avs type optical amplifier, TWA), Fabry-Perot optical amplifier (Fabry-Perot optical amplifier), which biases a normal semiconductor laser below its oscillation threshold and uses it as an optical amplifier.
type optical＾-plifier, F
P A), fiber Raman amplifiers that utilize stimulated Raman scattering in fibers, those that use DFB lasers, injection-locked amplifiers, etc. can be used, but semiconductor optical An amplifier is advantageous.

Among them, TWA is capable of high-speed response to electrical signals and amplification of high-speed optical signals, and because it does not have wavelength selectivity due to a resonator, it has a wide gain bandwidth of several + nanometers (about 50nm), and is sensitive to amplifier temperature and This has the great advantage that even if the wavelength of the incident light changes, the change in gain is small and a stable gain can be obtained. It also has excellent characteristics in terms of gain saturation and noise, which are important basic characteristics for an optical amplifier.

On the other hand, FPA has the advantage that it is easy to manufacture and can easily obtain a high gain near the threshold even with a low injection current because it obtains signal gain by utilizing multiple reflections between both end faces.

Furthermore, since the gain of a semiconductor optical amplifier can be easily changed by changing its injection current, it can also be used as an optical switch by turning on and off the injection current.

The operation of the above configuration will be explained based on the waveform diagram of FIG. 4.

As shown in FIG. 4(a), it is assumed that an optical pulse signal is input to the optical input terminal (20) at time t0. This optical pulse signal is split into two by a coupler (21).

Here, one optical pulse signal delayed by 18 hours as shown in (b) at the coupler (21) is further transmitted to the compensation delay path (21).
2), the optical switch (23
) to one input terminal (a).

Next, another optical trigger signal delayed by T1 time as shown in (C) by the coupler (21) is sent to the light receiving element (24) and output as an electrical pulse signal. This electrical pulse signal is amplified by an amplifier (25), passes through a timing control section (26), and is output from a waveguide driving pulse timing signal generator (26) as shown in (d) at time t1, a waveguide driving electrical trigger. A signal is output, and further a waveguide drive electric pulse signal is output from the waveguide drive pulse generator (28) at time t4. This pulse signal is delayed by a predetermined time in an electronic circuit from the light receiving element (24) to the waveguide driving pulse generator (28), and is output between the electrodes (35) (35) of the optical waveguide switch (23). Apply an electric field. Then, a negative refractive index barrier is formed along the electrodes (35) (35) in this optical switch (23), and the pulse signal is totally reflected, and the input/output terminals (a) → (d), The optical path from (b) to (c) is switched to the optical path from (a) to (c) and from (b) to (d).

Then, the optical pulse signal of (b) is transmitted to the optical switch (23
) is being switched, so it is sent to one output terminal (C), via the optical fiber (36a), and then to the optical amplification element (32) with a slight delay, as shown in (h). .

In addition, according to the timing signal from the timing control section (26), the optical amplifying element driving pulse timing generator (29) outputs an optical amplifying element driving electric trigger signal at times t as shown in (f), and furthermore, a little more. At the delayed time t1, an electric pulse signal is output from the optical amplification element driving electric pulse generator (30), the optical amplification element (32) operates, and the input optical signal is amplified like the pulse at t1 in (h). do.

Once the optical pulse signal is input to the delay path (31), the electrical signal to the optical switch (23) disappears while it is being input, so the other optical input terminal (b) → one optical output terminal (c)
→ It is confined in the closed circuit of the delay path (31) and circulates through this closed circuit many times.

While circulating in the closed circuit, an electric trigger signal and an electric pulse signal are output as shown in (f) and (g), and the optical amplification element (32) is activated each time, as shown in (h). amplify. This amplification degree may gradually increase and be saturated in the middle, or it may be always amplified at the same amplification degree.

As shown in the second half of (d), the waveguide driving pulse generator (28) is delayed by the delay time set by the timing controller (26), that is, by the delay time circulated in the optical delay path (31). The waveguide driving electric pulse signal is sent again, the optical switch (23) is switched as shown in the second half of (e), and the amplified optical pulse signal is transferred from the other optical input terminal (b) to the other optical output terminal (d). ) and output to the outside.

The above delay time t is given by t=N-n-jl/C. Here, N: the number of times the optical pulse signal circulates in the closed circuit, n: the refractive index of the optical fibers (36a) (36b), Q: the length of the delay path (31), and C: the speed of light.

In addition, in Fig. 4, the time width (τ1) of the optical pulse signal
must be sufficiently shorter than the unit delay time for passing through the closed circuit once. Further, the time width (τ2) of the electrical signal of the optical switch (23) needs to be equal to or less than the unit delay time. However, there is no problem even if the pulse width is large, as long as the falling edge of the optical pulse signal is controlled when it is introduced, and the rising edge of the leading edge is controlled when it is extracted.

In the embodiment described above, in FIG. 3, the other optical input terminal (
b) and one of the optical output terminals (c) are connected through the optical delay path (3) to form a closed circuit, so the optical switch (23) has two connections between confinement and output, as shown in Figure 4(e). The delay time was controlled by two pulses. However, the invention is not limited to this. For example, when the other optical input terminal (b) and the other optical output terminal (d) are coupled by an optical delay circuit (31), the optical pulse signal is transmitted once. The optical switch (23) may be switched to perform total reflection at the same timing every time the light goes around.

In the above embodiment, one optical switch (23) and one closed circuit optical delay M (31) were used, but the invention is not limited to this.For example, as shown in FIG. )
Or, in the same element, second, third, etc. optical switches (23b) (23c) are vertically connected in series with the first optical switch (23a) and the optical amplification element (32), Also,
Between the input side (b) of the first optical switch (23a) and the output side (d) of the second optical switch (23b), there is a first delay path (3
1a), and the input side (b) of the first optical switch (23a) and the output side (d) of the third optical switch (23c).
), and a third delay path (31b) is connected between the input side (b) of the first optical switch (23a) and the output side (c) of the third optical switch (23c). optical delay path (3
1c) to form first, second and third closed circuits of different lengths. And the first. Second. Third light switch (
By controlling the switching timing of 23a), (23b), and (23c), any combination of delay times can be achieved.

"Effects of the Invention" Since the present invention is configured as described above, it has the following effects.

(1) Optical amplification elements can compensate for optical losses caused by waveguide input/output, optical fiber transmission, coupling between optical fibers and other elements, condensing lenses, etc.

Therefore, long optical delays are possible.

(2) Arbitrary optical delay can be achieved using the optical fiber delay time as a unit.

(3) Unit delay time is optical fiber length and waveguide length.

It can be freely set by setting the condenser lens length and optical amplification element length.

(4) By configuring the device using an optical waveguide type optical switch, an optical fiber, and an optical amplification element, the device can be made small and extremely lightweight.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an optical pulse signal delay device according to the present invention, FIG. 2 is an explanatory diagram of an optical waveguide type optical switch, and FIG. 3 is an explanatory diagram of an optical delay path. FIG. 4 is a waveform diagram, FIG. 5 is an explanatory diagram of another embodiment of the present invention, FIGS. 6, 7, and 8 are explanatory diagrams of different conventional examples, and FIG. 9 is an illustration of an optical β element. An explanatory diagram, FIG. 10, is an explanatory diagram of a voltage-controlled optical directional coupler. (1) Coupler, (1a) Beam splitter, (2) Light receiving element, (3) Trigger circuit,
(4)... Optical pulse measuring device, (5)... Optical fiber, (6)... Prism, (7)... Optical β element, (8)... Optical line, (9) ...Optical delay line. (10)...Input terminal, (11)...Output terminal, (
12)...Light absorber, (13)...Control terminal, (1
4)... Electro-optic crystal substrate, (15) (16)...
・Optical guide line, (17)...control electrode, (18) (1
9)...electrode, (20)...input terminal, (21)...
・Coupler, (22) ・Compensation optical delay path, (23
)...Optical waveguide type optical switch, (23a) (23b
) (23c)... Optical switch, (24)... Light receiving element, (25)... Amplifier, (26)... Timing control section, (27)... Waveguide drive pulse timing signal generation (28)... Waveguide drive pulse generator, (29)... Optical amplification element drive pulse timing generator, (30)... Optical amplification element drive pulse generator, (3
1)... Optical delay path, (31a)... First delay path,
(31b)...second delay path, (31c)...third delay path
optical delay path, (32)...optical amplification element, (33) (
33)...Waveguide. (34)--Intersection, (35) (35)--Parallel electrode, (36a) (36b)--Delay optical fiber, (37a) (37b)--Condensing lens, (38 )
... Optical signal output terminal, (39) ... Same board,
(a) (b)... Optical input terminal, (c) (d)...
Optical output terminal.

Claims (4)

[Claims] (1) An optical switch having at least two optical input terminals and at least two optical output terminals and capable of switching the optical path between these input and output terminals, and at least one input and output terminal of this optical switch coupled It is characterized by comprising a delay optical fiber, an optical amplification element inserted in the middle of the delay optical fiber, and a timing control section that outputs a switching control signal for the optical switch to set a delay time. Optical pulse signal delay device. (2) An optical switch is a total reflection type optical waveguide type optical switch that switches the optical path by forming a negative refractive index barrier and total reflection when an electric field is applied to an electrode, and it converts optical pulse signals into The optical pulse signal delay device according to claim 1, wherein the optical pulse signal delay device is operated when being introduced into the device and when being led out. (3) The optical pulse signal according to claim (1) or (2), wherein the delay optical fiber forms a delay path together with an optical amplification element, and the unit delay time is determined by adjusting the length of this delay path. delay device. (4) Claim (1) in which a condensing lens is interposed on the optical pulse input/output side where the optical amplification element and the delay optical fiber are coupled.
), (2) or (3).