JPH08271945A - Configurating method for optical functional circuit - Google Patents

Abstract

PURPOSE: To provide an optical function circuit attaining various logical functions only by an optical signal by connecting an active optical fiber or an optical waveguide which acts to amplify signal light by exciting light in two-stage longitudinal connection. CONSTITUTION: Erbium dope optical fibers 1 and 2 are connected in longitudinal lines in two stages. The signal light S (input A) and the exciting light P are made incident on a coupler 3. The signal light S is amplified in the optical fiber 1 and the excitation light P is attenuated. The signal light S passes through an isolator 4, is separated by a filter 5 and taken out as output A. The 2nd signal light (input B) is made incident on the optical fiber 2 at the 2nd stage through a coupler 6 together with the excitation light P transmitted through the 1st stage. Since the amplification degree of the input B is nearly proportioned to the power of the incident excitation light P, the input B is more largely amplified when the signal light S does not exist at the 1st stage, for example. Then, it is allowed to pass through an isolator 7 and separated by a filter 8 to be made output B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a novel optical functional circuit having a logical operation by using an optical fiber or an optical integrated circuit active to light, which is necessary for logical processing of optical signals. And a processing device. Since this optical circuit can operate at high speed, it can be used in applications where high speed is particularly required, that is, in fields such as direct optical signal processing in optical communication, optical computers, and optical image processing.

[0002]

2. Description of the Related Art Due to recent developments in optical communication and optical information processing technology, direct signal processing is performed as it is, instead of performing signal processing after converting an optical signal into an electrical signal. The need has arisen. However, in the conventional optical device, it was difficult to achieve all the logical functions only with the optical signal. Therefore, in order to perform such a function by a conventional device, it is necessary to partially incorporate an electronic circuit. With this method,
It is necessary to repeatedly perform signal conversion of <light → electricity> and <electricity → light>, which is not only troublesome in designing and creating the system, but also depends on performance such as operation speed of each conversion element. It had its own speed limit.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method of constructing an optical functional circuit which achieves various logical functions only by an optical signal which has been difficult to realize until now. And Specifically, it is to provide a novel optical circuit having a NOT function, a pseudo AND function, and a function that can be achieved by combining them. In addition, this optical functional circuit uses an extremely fast quantum phenomenon called transition of electron orbits in a material,
The operating speed will depend only on the dispersion characteristics of the optical fiber and the optical waveguide. In fact, dispersion can be ignored by using an optical fiber with zero dispersion characteristics or an optical fiber that is sufficiently short, so that it is possible to perform extremely high-speed logical operation and not only meet the latest needs. Therefore, it can be expected that it will be able to meet future demands for ultra-high-speed optical signal processing. In principle, the photochromic effect, which is colored when irradiated with light, also has the characteristic of NOT, but its response speed is slow and it is not practical at present.

[0004]

SUMMARY OF THE INVENTION The present invention provides a signal light to an optical fiber or a waveguide having an active region doped with an active substance such as erbium (Er), neodymium (Nd), paratheodium (Pa), YAG. In addition, an optical amplifier that amplifies the signal light by inputting the pumping light is used, and by connecting the two in two stages with respect to the optical path of the pumping light, the output of the second stage is
It is a configuration method of an optical functional circuit, which is configured to obtain an inverted waveform of a signal waveform applied to a stage. Further, it is also possible to form an optical oscillator in which the interval between the optical pulses can be made desired by using this construction method.

[0005]

According to the present invention, the active optical fibers or the optical waveguides having the function of amplifying the signal light by the pump light are connected in two stages in cascade, and the pump light that has been attenuated depending on the power of the signal light in the first stage has two stages. By introducing into the eye, the NOT function can be realized by utilizing the fact that the amplification degree of the optical signal newly added to the second stage is affected by the signal added to the first stage and the signal waveform is inverted. Further, the inverted signal becomes a pseudo AND with the signal added in the first stage.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method of constructing an optical functional circuit of the present invention will be described below with reference to the drawings. Figure 1 shows erbium (E
r) It is a block diagram which shows the structure of the optical functional circuit comprised by the doped optical fiber. That is, the configuration of this optical function circuit is
It is mainly configured by connecting Er-doped optical fibers 1 and Er-doped optical fibers 2 in two stages in tandem. A coupler 3 is coupled to the incident end of the Er-doped optical fiber 1 of the first stage, and an input signal light S (input A) having a wavelength of 1.55 μm and a pumping light P having a wavelength of 0.51 μm are made incident. Since the Er-doped optical fiber 1 is doped with the active substance Er, E
Due to the quantum effect of the r atom, the signal light S has a wavelength of 0.
It acts to remove energy from the excitation light of 51 μm. Therefore, the signal light S is amplified and the pumping light P is attenuated as it propagates through the Er-doped optical fiber 1. At this time, the amount of attenuation of the pumping light P depends on the initial incident power (P _SO ) of the signal light S. That is, if there is no signal light S (that is, P _SO = 0), the pumping light is emitted in a state where it is not much attenuated. The signal light S passes through an isolator 4 that blocks reflected light, and then is separated by a filter 5 that uses a distributed coupler having wavelength dependence, and is taken out as an output A having a wavelength of 1.55 μm.

Next, the coupler 6 is connected to the other output end of the wavelength dependent coupler 5 and the incident end of the Er-doped optical fiber 2 at the second stage is connected. In this second stage, the wavelength is 1.5
The second signal light of 5 μm (also called strobe light) is input as B and is incident together with the pumping light P transmitted through the first stage to generate the same optical amplification effect as in the first stage. In this case, since the amplification degree of the input B is almost proportional to the incident pumping light power, if the signal light power of the first stage is large,
The excitation light is greatly attenuated, and the amplification degree in this second stage is small.

However, if there is no signal light S in the first stage, the pumping light P has sufficient power to enter the second stage, and amplifies the input B to a greater extent. Similarly to the above, this is separated from the pumping light component (wavelength 0.51 μm) through the isolator 7 and the wavelength-dependent distribution coupler 8 to obtain the output B of wavelength 1.55 μm.

This series of operations qualitatively has a signal light (input A) between the magnitude of the signal power input first and the power of the output signal B → output B is small, but no signal light (input A) → The output B is large. This is a logical operation

It means the operation of the logic element [External 1]. if,
First if you have multiple input signals

This corresponds to the operation of the element of [External 2].

[Outside 1]

[Outside 2]

Since this operation does not occur without the strobe light (input B), it can be seen that the strobe light (input B) serves as a switch. In other words, if you do not want to operate this circuit, strobe light (input B)
Is turned off (off), and the strobe light (input B) is turned on (on) only when it is desired to operate.

When the strobe light is input B, the output B can be written by the following logical expression. Output B =

[Outer 3] × input B where:

[Outer 4] means inversion. X means AND. In this equation, one is inverted, so it is not a pure AND. This is called pseudo AND, but this circuit is pseudo A
It is also ND.

[Outside 3]

[Outside 4]

Further, the output A and the output B are in a complementary relationship, and the circuit shown in FIG. 1 has a so-called multi-output. This is a useful feature for constructing more complicated circuits.

Next, another embodiment will be described with reference to FIG. In the above embodiment, the optical fiber doped with the active substance is described, but this example uses the waveguide doped with the active substance. That is, the optical function circuit 10
Is a coupler 11 for mixing the signal light S (input A) and the pumping light P, and a first active region 1 doped with an active material.
2, a wavelength-dependent distributed coupler 13 for separating a signal light component and extracting an output A, and a coupler 14 for mixing new signal light (input B) and pumping light that has passed through the first active region, The second active region 15 and the wavelength-dependent distributed coupler 16 for separating and extracting the signal light component are included. In this example, branch couplers are used as the coupler 11 and the coupler 14 for mixing the signal light and the pump light. A distributed coupler is used as a filter for extracting the signal light, and a coupling efficiency close to 100% is obtained. In this example, as the waveguide material, a quartz substrate was doped with Ge in the waveguide portion, and the active material had a wavelength of 1.55.
Er is used for a signal of μm and Pa is used for a signal of wavelength 1.3 μm.

The operation of this embodiment will be described. Coupler 11
The excitation light P and the signal S are incident on the two incident ends of the above, and mixed, and the signal light S is amplified by the first active region 12 and extracted as the output A by the wavelength dependent coupler 13. on the other hand,
The pumping light P is attenuated, but in this case as well, as in the previous example, when the signal light S is large in the first stage, the pumping light P is attenuated and enters the second active region 15. The amplification degree at 2 becomes small and the output B becomes small. Further, when there is no signal light S to the first stage, the attenuation of the pumping light P also becomes small and a large amplification degree is obtained in the second active region 15, so the output B becomes large.

The example shown in FIG. 2 is an example in which the waveguide doped with the active substance is divided and provided, but the example shown in FIG. 3 is constituted by one continuous active region 22. . That is, the optical function circuit 20 uses the signal light S (input A)
And a pumping light P, a coupler 21, an active region 22 doped with an active substance, a wavelength-dependent distributed coupler 23 for extracting an output A provided in the active region 22, and a new It is composed of a coupler 24 for mixing the signal light (input B) and the excitation light that has passed through the first active region 22 and a wavelength-dependent distribution coupler 26 for separating and extracting the signal light component. This operation is completely the same in principle as that shown in FIG.

Next, FIGS. 4A and 4B show an equivalent circuit in which the present optical function circuit is represented as a logic element. FIG.
(A) corresponds to the basic configuration of the optical functional circuit, and is shown in FIG.
(B) is an example in which the OR function is achieved by making the inputs plural. Multiple inputs can be achieved by cascading multiple couplers used for mixing.

Next, FIG. 5A shows an example of an optical oscillator constituted by the present optical function circuit. That is, the optical fiber 31 having the length L is provided between the input end A and the output end B of the optical function circuit 30.
By connecting with, it is possible to oscillate with a waveform as shown in FIG. 5B at pulse intervals determined by a time lag proportional to the length of the optical fiber 31.

The operation of this functional circuit is as follows. That is, when the pumping light and the strobe light are given, since there is no light at the input end A, light having a large power is output from the output end B. However, since the input end A and the output end B are connected by the optical fiber 31, the light reaches the input end A after the time τ has elapsed. (Here, τ is the propagation delay time of the optical signal propagating through the optical fiber 31, and can be calculated from τ = n _eff · L / c. N _eff is the effective refractive index of the optical fiber 31,
L is the length of the optical fiber 31, and c is the speed of light in a vacuum. Then, this time, the action of suppressing the output B occurs by the NOT function as described above. As a result, if the optical power of the output B becomes weaker, the power at the input A becomes smaller again after the time τ has elapsed, and a large output is generated this time due to the inversion. This operation always occurs with a deviation of τ between the input end A and the output end B, and therefore oscillates with a waveform as shown in FIG. 5B.

[0019]

As described above, according to the method of constructing an optical functional circuit of the present invention, it becomes possible to construct an optical circuit capable of directly processing an optical signal, and the application range of the optical signal processing technique is greatly expanded. It can make excellent contribution to the development of optical communication and optical information processing technology.

[Brief description of drawings]

FIG. 1 is an optical circuit configuration diagram of an embodiment showing a method for constructing an optical functional circuit of the present invention,

FIG. 2 is an optical circuit configuration diagram of another embodiment,

3 is an optical circuit configuration diagram of a modified example of FIG.

4A and 4B are equivalent circuit diagrams of an optical functional circuit of an embodiment,

5A is an equivalent circuit diagram when applied to an optical oscillator, and FIG. 5B shows an output waveform of the oscillator.

[Explanation of symbols]

 1, 2 Optical fiber doped with active substance 3, 6, 8 Coupler 4 Isolator 5, 7 Wavelength dependent distributed coupler (filter) 10, 20, 30 Optical functional circuit 11, 14 Coupler 12, 15 Active region 13, 16 Wavelength dependent distributed coupler (filter) 21,24 Coupler 22 Active region 23,26 Wavelength dependent distributed coupler (filter) 31 Optical fiber

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yumi Ariga 2-1-1, Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Showa Cable Denki Co., Ltd.

Claims (5)

[Claims] 1. An optical amplifier for amplifying a signal light by making the excitation light incident on the optical fiber or the optical waveguide doped with an active substance together with the signal light, and connecting the two in two stages with respect to the optical path of the excitation light. In the above configuration, the optical function circuit is configured so that the inverted waveform of the signal waveform applied to the first stage is obtained at the output of the second stage. 2. An optical circuit based on the method of constructing an optical functional circuit according to claim 1, wherein a coupler for mixing two wavelengths, a first optical amplifier, a reflected light blocking isolator, and a signal light removing filter by a wavelength dependent coupler are used. , A second two-wavelength mixing coupler, a second optical amplifier, a second isolator, and a second wavelength-dependent coupler are connected in this order, and the input signal waveform to the first stage and the output signal waveform of the second stage are connected. A NOT logic element characterized in that it is configured by utilizing the fact that there is an inversion relation. 3. An optical circuit based on the method of constructing an optical functional circuit according to claim 1, wherein a coupler for mixing two wavelengths, a first optical amplifier, a reflected light blocking isolator, and a signal light removing filter by a wavelength dependent coupler are used. , A second two-wavelength mixing coupler, a second optical amplifier, a second isolator, and a second wavelength-dependent coupler are connected in this order, and the output of the second stage is logically connected to the input signal of the first stage. A logical element characterized by having a pseudo AND relationship. 4. An optical circuit based on the method of constructing an optical functional circuit according to claim 1, wherein a coupler for mixing two wavelengths, a first optical amplifier, a reflected light blocking isolator, and a signal light removing filter by a wavelength dependent coupler are used. , A second coupler for mixing two wavelengths, a second optical amplifier, a second isolator, and a second wavelength-dependent coupler are connected in this order, and the waveform of the input signal to the first stage and the output of the second stage are connected. A waveform converter characterized by utilizing the fact that signal waveforms are in an inverted relationship. 5. An optical oscillator characterized in that the pulse interval can be adjusted as desired by connecting optical fibers of different lengths to the NOT logic element of claim 2.