JPH01234819A - Light delay generator - Google Patents

Abstract

PURPOSE:To improve resolution and to control the delay of a light signal with high accuracy by applying a voltage to an electrooptic crystal body, and varying its refractive index to light with the voltage and varying the length of an optical path. CONSTITUTION:The voltage is applied between a lead-out wire 14 and an electrode 13 and varied to control the delay time of a light signal which passes through the crystal body 8. Namely, the light passed through a half-mirror 2 varies in refractive index with the voltage from a voltage applying circuit 9, and consequently the optical path of the light becomes long, so that the light is delayed finely and projected from the crystal body 8. The projecting light is sent to a receiving circuit 22 through a half-mirror 5 and a PIN photodiode 19, so the receiving circuit 22 receives two light pulses which have a fine time interval. At the time interval of the light pulses, the light pulses are accurately received with high accuracy without any variation in pulse width. Consequently, the high-accuracy, high-resolution light delay generating circuit is obtained.

Description

[Detailed Description of the Invention] [Summary] Regarding a delay generator for optical signals, the purpose is to control the delay of No. 11 with high resolution and high precision, and an electro-optic crystal,
An electrode for applying a voltage to the crystal body is provided, and by controlling the voltage applied to the electrode, the optical path length of the light propagating within the crystal body is changed, and the light propagation flj! It consists of an optical delay generator that is characterized by changing the delay time.

[Industrial application field]

The present invention relates to an original signal delay generator. Optical communication technology that uses light for information transmission has made remarkable progress in recent years, and has already been put into practical use in many fields. In the field of optical communications, technology for controlling optical delay with high resolution and high n-degrees has become one of the important technologies.

[Conventional technology]

FIG. 5 shows an example of the configuration of a conventional optical delay generation circuit.

When the original pulse signal emitted from the laser generator 1 reaches the half mirror 2, it is separated into reflected light and transmitted light, and the reflected light is further reflected by mirrors 3 and 4 and transmitted through the half mirror 5 to become transmitted light a. The light is then received by the optical receiver 7. Note that a part of the light that has passed through the half mirror 2 further passes through the half mirror 5, goes straight to the mirror 6, is reflected by the mirror 6, returns along the path shown by the dotted line, and is partially reflected again by the half mirror 5. It becomes a reflection 2b and is received by a light receiver.

Here, a slight delay occurs between the light a received by the light receiver 7 and the light beam, and this delay time can be adjusted by mechanically moving the mirror 6 back and forth.

[Problem a that the invention attempts to solve]

The above conventional technique moves the mirror mechanically, and therefore has difficulties in terms of reproducibility and stability.

The present invention solves the above-mentioned conventional problems, and aims to provide a technique that can control the delay of an original signal with high resolution and high precision.

[Failure to solve the problem]

FIG. 1 is a diagram explaining the principle of the present invention.

While the source emitted from the source generator 1 passes through the electro-optic crystal 8, α is applied to the crystal 8 from the voltage application circuit 9.
The pressure causes a change in the refractive index and changes the optical path length of the light, resulting in a delay before the light is emitted from the crystal body 8.

[Effect]

In the present invention, as shown in Figure 1, a vL electro-optic crystal voltage is applied, and the refractive index of light is varied depending on the value of this voltage to change the optical path length of the light, so that the light passes through the crystal 8t. adjusting the time.

〔Example〕

FIG. 2 is a configuration diagram of an embodiment of the present invention.

8 is an electro-optic crystal, KDI) (KH, PO4
).

ADP (NR1R2P O4), L i Nbo
, , L+Tao, , GaAs, and other crystals are known.

An electrode 11 formed by vapor deposition of aluminum or the like is broken on the upper surface of this crystal body 8, and a metal electrode 13 is formed on the lower surface.A dielectric multilayer film is formed on the light incident surface. An antireflection film 12 is applied.

A voltage is applied between the lead wire 14 and the electrode 13, and by changing this voltage, the delay time of the optical signal passing through the crystal body 8 is adjusted.

The light incident on the crystal body 8 is linearly polarized light 15, and the polarization direction of this linearly polarized light is parallel to the birefringence @y (birefringence $ellipsoid principal axis) induced by applying a voltage to the crystal body 8. When the light 15 is made incident such that the refractive index change Δn is proportional to the applied voltage.

If the physical length of the crystal 8 is l and the speed of light is C, then
The time it takes for the element to pass through the crystal is Δ(=Δn6 l/c (11
only changes.

The relational expression between Δn and the applied voltage ■ is the following if'l.

Here, the crystal is a 43III type crystal (GaAs
.

InP, etc.), where no is the ordinary refractive index and γ4. is the Pockels constant, and d is the thickness of the crystal.

FIG. 3 shows an embodiment of an optical delay generation circuit adapted to the optical delay generator of the present invention.

16 is a power supply circuit, and 17 is a pulse laser generating circuit composed of a semiconductor laser or the like. Trigger signal generation circuit 20
A narrow linearly polarized light pulse is emitted from the pulse laser generating circuit 17 in response to a trigger signal from the pulse laser generating circuit 17.

This light is separated by half mirror 2, and the reflected light is reflected by mirror 3.
．． 4't-, the reflected light reaches the half mirror 5, and the reflected light reaches the PI
The signal is received by the N photodiode 19, converted into an electrical signal, and sent to the receiving circuit 22.

On the other hand, the light that has passed through the half mirror 2 passes through the electro-optic crystal 8, but during this time the refractive index changes due to the voltage from the voltage application circuit 9, which lengthens the optical path of the light and causes a slight delay in the optical signal. It is received and emitted from the crystal body 8. This emitted light reaches the half mirror 55, and the transmitted light is received by the PIN photodiode 19, converted into an electrical signal, and sent to the receiving circuit 22.

Therefore, the receiver A3 circuit 22 receives two original pulses having a minute time width.

By controlling the voltage 1fL applied to the crystal body 8 from the voltage application circuit 9, the time interval of the original pulse can be received accurately and with high resolution without any change in pulse width.

FIG. 4 shows an optical delay generator according to another embodiment of the present invention, in which a reflective film is deposited on two sides of an electro-optic crystal body 8, and a reflective film is deposited diagonally from a part of the crystal body 8 that does not have a reflective film. The incident light travels inside the crystal body 8 while being reflected many times, and is emitted from the other part where there is no reflective film. In this case, crystal 8
It is possible to increase the actual length through which the signal passes through, making it possible to control a greater delay time. Although the above embodiment uses a bulk crystal, it is also possible to obtain an extremely small optical delay generator using a waveguide structure. Further, the electro-optic crystal structure is not limited to the above structure, and crystals having other structures can be used.

〔Effect of the invention〕

As described above, according to the present invention, a highly accurate and highly resolved optical delay generation circuit can be realized.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, FIG. 3 is a block diagram of an embodiment of an optical delay generation circuit to which the optical delay generator of the present invention is applied, and FIG. 4 is a block diagram of another embodiment of the present invention, and FIG. 5 shows a conventional optical delay generation circuit. In the figure, 1 is the original light emitter, 2.5 is the half mirror 13,
4 is a mirror, 8 is an electro-optic crystal, 9 is a voltage application circuit,
11° 13 is an electrode, 12 is an antireflection film, 15 is incident light,
16 is 1! 17 is a pulse laser generation circuit, 19 is P
IN photodiode, 20 trigger signal generation circuit, 2
2 is a receiving circuit, and 23 is a reflective film. This invention f) Kuzujiri crime calculation 1st invention/) Laughter retro 1 Pierreme drama% 2 memories 4 figures

Claims (1)

[Claims] An electro-optic crystal 10 and electrodes 11 and 13 for applying voltage to the crystal are provided, and by controlling the voltage applied to the electrodes 11 and 13, the optical path length of light propagating within the crystal is changed. An optical delay generator characterized by changing the propagation delay time of light.