JPH02212822A - Coherent signal processor - Google Patents

Abstract

PURPOSE:To couple a light signal coherently and to utilize the speediness and band broadness of an optical waveguide by combining variable branching devices and phase shifters and performing optional weighting. CONSTITUTION:The variable branching devices S0, S1... Sn-1 distribute light signals which have electric field amplitudes at an optional branch ratio to respective taps and the branch ratio shows the absolute value of the weighing coefficient of each tap. The light signals which are distributed to the respective taps are phase-shifted optionally by the phase shifters P0, P1... Pn-1 and added after being multiplied not only non-negative real number coefficients, but also by optional weighting coefficients including complex numbers. Consequently, the signal processor which enables coherent coupling by using the optical waveguide as a delay line is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a coherent signal processing device using a delay line formed of an optical waveguide.

<Prior Art> Optical waveguides, particularly optical fibers, have a wide range of uses, including transmission lines for optical communication networks, due to their high speed and broadband properties. In particular, when used as a delay line for information processing, it is advantageous for processing high-speed optical signals with a wide passing frequency band. The use of single mode optical fibers as delay lines for signal processing in this way has already been proposed by IEEE
ns on Microwave Theory an
dTechniques MTr Volume 33, No. 3 r 0ptical fiber delay-
It is proposed in a paper entitled 1ine signal proessingJ. The tapped and recirculating delay lines described herein incoherently combine optical signals from each of the taps connected to the delay line. That is, as shown in FIG. 8, which shows an example of the configuration of a tapped delay line, an optical signal from a light source 1 that emits continuous light waves is modulated by an optical intensity modulator 2 and guided to a delay line composed of a leading waveguide 3. It will be destroyed. This optical signal is sent to equally spaced branches @D0. along the delay line. D,, D,,・
. . D, , -, each tap T0. T,, T
2. ...T,, -1, variable attenuation @W0.
W,, W2. . . . The signal is attenuated to a predetermined value by W, , -1, and added to the adder 6 with Yinko and -shift. Further, as shown in FIG. 9, which shows an example of the configuration of a recirculating delay line, the optical signal from the light source 1 that emits continuous light waves has a light intensity change of i! ! The signal is modulated by a J-device 2 and guided to a delay line constituted by an optical waveguide 3. This optical signal was introduced into the input end of the directional coupler 8, and circulated through a delay line provided between the output end d and the input end a (incoherently coupled with No. 1, and the combined signal is taken out from the output terminal C and detected by the optical detector 5.

<Problems to be Solved by the Invention> However, the above-mentioned conventional technology combines each signal incoherently, and can only realize non-negative real coefficients as weighting coefficients for taps, which imposes restrictions on signal processing. Ta. For example, it is not possible to obtain high-pass filtering characteristics in the frequency characteristics, and it is not possible to perform differential calculations on the time axis.

The present invention has been made in view of the above-mentioned prior art, and it is an object of the present invention to provide a signal processing device capable of coherent coupling using an optical waveguide as a delay line.

Means for Solving the Problems> The coherent signal processing device of the present invention uses an optical waveguide as a delay line, has a plurality of taps arranged in series or in parallel, and has an electric field amplitude of an arbitrary branching ratio applied to each tap. A variable splitter that distributes the optical signal that has been distributed to each tap, a phase shifter that applies an arbitrary phase left to the optical signal distributed to the tap, and an optical coupler that coherently combines the optical signal. It is characterized in that the distributed optical signals are multiplied by arbitrary weighting coefficients and then added.

Function: The variable splitter distributes an optical signal having an electric field amplitude of an arbitrary branching ratio to each tap, and the branching ratio expresses the absolute value of the weighting coefficient of each tap.

The optical signals distributed to each tap are subjected to arbitrary phase shifts using phase shifts, multiplied not only by non-negative real number coefficients but also by arbitrary weighting coefficients including complex numbers, and then added.

Embodiments The present invention will now be described in detail based on embodiments shown in the drawings.

FIG. 1 shows an embodiment according to the first invention of the present application. As shown in the figure, an optical signal from a light source that oscillates continuous light waves is modulated by optical intensity modulation u2 and guided to a delay line constituted by an optical waveguide 3. Variable branches ll5o, S, , S, .""l-1 are arranged at equal intervals on the delay line, and the optical signal is transmitted to these variable branches S, , S, .
S.

...Electric field amplitude A0 for any branching ratio according to S. A.

A2...A, , -, as an optical signal having taps T,
, T, #T...T. Tap T0
~T, , can be connected to the delay line via n-1 variable branch -5o-S,1, while
Taps TI and T, which are connected in parallel to the optical coupler 4 and adjacent to each other.

, and the delay times τ of the delay lines are all equal. On the taps T0 to T- there is a phase shifter P0. P,, P
,...p, , are arranged respectively and the taps T0 to T,
The optical signals branched to −1 are each passed through a phase shifter P(+” t
An arbitrary phase shift is applied by "2...Pn-1. Then, the optical signals are combined by optical coupling M4.

Here, the optical signal is a high frequency with a frequency F of about Z The phase of the branched optical signal is left depending on the position on the delay line where tapping is performed and the position where each tap T0 to T- is connected to the optical coupler.

~5n-1, optical coupling! ! The phase is also shifted when passing through g4. For this reason, the phase shift g p, .

In a conventional tapped delay line that does not have Pl, P,...P7-1, the coupled optical signal is shifted by one phase, but in the present invention, a phase shifter P placed on each tap is used.
0 to Po4, an arbitrary phase shift G is applied so as to cancel out the phase difference of the optical signals between the taps coupled by the optical coupler 4.
#1. Each phase shifter P0-P. The desired phase shift is applied by −1 respectively θ. , θ8. θ2...θ
. , then the weighting coefficient applied to the optical signal passing through each tap is a. wAoexp(jθ.), a, =A
,exp(jθ,).

a2=A, exp(jθ,) ・-a,-,=A,,-
, axp(jθo−1).

Therefore, the output optical signal "aut(t)" which is combined by the optical coupling 94 and detected by the optical detector 5 is obtained by multiplying the branched optical signal by a weighting coefficient of 80 to -8 and adding it as shown in the following formula. It becomes a combination.

However, the optical signals input to the delay line are assumed to be E, , (tl), and other conditions are omitted.

E, t, t (1=7°a, E, , (t-iτ)
・-(11 In order to simplify the explanation of equation (1), we will use the specific example of n-3 shown in FIG. Let the electric field amplitude of the ratio be A0=1/4, A,=
1/2, A, = 1/4, and the phase shift a p,
, p, , p, −p, l, , 1 with a phase shift of θ, respectively. =0. If θ, = π, θ2; 0, each tap T. , T,−,T2...T,,−1 are each weighted by a o :1/4 p′ i
;” It is expressed as 2pa2==174.Input optical signal E
,, (t), amplitude l, angular frequency ω (= 2+rf
), if we use an optical signal modulated with a sine wave of (
Equation 11 can be simplified as shown below. However, Ω; 2πF
It is.

E engineering Jtl = Σ tag e to p (j (ω + Ω) (t-iτ))
=-”exp(j(ω+Ω)t) 2-”p(j(ω
+ΩHt-)), 1 shi 4' e field 1j (b juice Ω) (t-2τ)) =->-
exp (j (ω+Ω)(1-τ)) (1-am(
ω + Ω) τ) = exp < j (ω + Ω) (tr)
)mx(f+F)r -12) In this way, in the present invention, the weighting coefficient can be negative, so the optical signal can be coherently coupled to the optical coupler. Therefore, signal processing that is impossible with conventional incoherent combinations can be performed.

For example, the frequency characteristic of a signal processing device having the configuration shown in FIG. 5 is expressed by the following equation, and has a high-pass filtering characteristic, that is, a differential characteristic, as shown in FIG.

16,,-I Eou 淋)12 =-π(f+F)r...(3
) Therefore, if a multiplexed signal of high frequency and low frequency as shown in FIG. 7 (al) is input, only the high frequency is filtered and obtained as an output signal as shown in FIG. 7 (bl).

On the other hand, the variable branch ll! As a specific example of the phase shift group, those shown in FIG. 4 may be used. As the variable splitter, as shown in FIG. 4 (Jl), an optical switch is used that utilizes the Ti1l optical effect by providing an electrode 43 at the coupling part of the directional coupling 11g41, and the optical waveguide 4
The outputs ■ and ■ of 2 are as shown in the same figure (b). In addition, as a phase shifter, an optical waveguide 4 is used as shown in FIG. 4(e).
A phase modulator is used which utilizes the electro-optic effect by providing an electrode 43 on the optical waveguide 2, and its optical phase is as shown in FIG. 2(d).

Next, the second part of this application. The third invention will be explained with reference to the embodiments shown in FIGS. 2 and 3.

First, in the embodiment of the second invention shown in FIG. 2, an optical signal from a light source 1 that oscillates continuous light waves is modulated by an optical intensity modulator and input to a variable branch gs. There is a tap T on the variable turnout S. .

T,,T,...T, are connected in parallel, and the variable branch S
is the electric field amplitude A0. of the signal inputted in time series at an arbitrary branching ratio. A,, A2...A7-1 is branched into an optical signal and distributed to each tap T0 to T,..., I.

Taps T0 to To-I each have a delay amount O2τ.

2r, . . . (n-1)r, each having a phase shift θ0 . θ8. θ
2... θn-1 phase shifter P0. P.

P2...Po-, are arranged. Tap T0~T
, l-.

are connected in parallel to optical coupling #s4, and each tap T to T, ,
(No. 1 is the weighted coefficient a.=
A. exp(jθ.), a,=A,exp(jθ,
).

a2=to2exp (jθ,)-6,-,=A,-,e
The signals are multiplied by xp(jθ.-1) and added by the optical coupler 4 as shown in equation (1) above, coherently combined, and detected by the optical detector 5.

Further, the embodiment of the @3 invention shown in FIG. 3 is designed to return coherently coupled optical signals.

That is, in the same manner as the embodiment shown in FIG. S,...Sr+-1'
Phase shift lL? p0゜P, . . . p, , -, tap T. , T
, . . . T, , 4, etc., the optical signals are coherently combined by the optical coupling wj4, and this is further combined with the optical signal output from the light R1 and modulated by the optical intensity modulator 2.

The embodiment of FIG.
The embodiment shown in FIG. 2 may be referred to as an acyclic configuration.

<Effects of the Invention> As specifically explained based on the embodiments, the present invention provides a variable splitter in a signal processing device using a delay line consisting of a leading wavepath.

By combining phase shifters and performing arbitrary weighting, optical signals can be coherently combined. Therefore, signal processing functions that were impossible with conventional incoherent coupling can be realized. Due to this, φ, the high speed of the optical waveguide,
It is possible to make full use of the broadband property, and it can be applied to a wide range of applications such as optical information processing and optical communications.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment according to the first invention of the present application, and FIG.
The figure is a block diagram of an embodiment according to the second invention of the present application, FIG. 3 is a block diagram of an embodiment according to the third invention of the present application, and FIG. 4(a)
is a specific configuration diagram of the variable turnout; bl is the same diagram (a
), the same figure (cl is a specific configuration diagram of the phase shifter, the same figure (di is a graph showing the optical electric field phase θ of the same figure (c), Fig. 5 is the same as Fig. 1) A configuration diagram showing a specific example in which n=3 in the example shown in FIG. 6 is a graph showing the frequency characteristics obtained by the configuration shown in FIG.
1 is a graph showing input signals and output signals to the signal processing device configured as shown in FIG. 5, FIG. 8 is a block diagram showing a conventional example of a non-cyclic type, and FIG. 9 is a conventional example of a cyclic type. FIG. In the drawing, 1 is a light source, 2 is a light intensity modulator, 3 is a leading waveguide, 4 is an optical coupler, 5 is a photodetector, 6 is an adder, 7 is a signal detector, 8 is a directional coupler, Do, D, . . . D, is branch-1 WC,, w, , . . w, , - is a variable attenuator, S6
t SH#...5n-1 is a variable splitter, To, T,
t-T,, is a tap, Po, P,...P,, -1 is a phase shifter, Ao, A,...
...A, -1 is the electric field amplitude of the optical signal distributed to each tap, θ. , θ2. ...on-1 is the amount of phase shift applied to each tap, a, b are input ends, c, ci are output ends, τ is unit delay time, 41 is a directional coupler, 42 is an optical waveguide, 43 is an electrode.

Claims (3)

[Claims] (1) A delay line consisting of an optical waveguide having an arbitrary amount of delay, a plurality of taps connected along the delay line, and an arbitrary branch arranged in cascade at the tapping position on the delay line and connected to the tap. a plurality of variable splitters that distribute delayed optical signals having electric field amplitudes of a ratio of 1 to 2; What is claimed is: 1. A coherent signal processing device comprising: an optical coupler that coherently couples the optical signals of the taps, and the device multiplies the optical signals distributed to each tap by an arbitrary weighting coefficient and adds the multiplied signals. (2) A plurality of taps arranged in parallel, a variable splitter that distributes an optical signal having an electric field amplitude with an arbitrary branching ratio to the taps, and an optical guide arranged on the taps and each having a different arbitrary delay amount. A delay line consisting of a wave path, a plurality of phase shifters placed on the tap and applying arbitrary phase shifts to the optical signals distributed to the tap, and an optical coupler that coherently combines the optical signals of the taps. A coherent signal processing device characterized in that the optical signals distributed to each tap are multiplied by arbitrary weighting coefficients and added together. (3) A delay line consisting of an optical waveguide having an arbitrary amount of delay, a plurality of taps connected along the delay line, and an arbitrary branch arranged in cascade at the tapping position on the delay line and connected to the tap. a plurality of variable splitters that distribute delayed optical signals having electric field amplitudes of a ratio of 1 to 2; It is equipped with an optical coupler that coherently combines the optical signals of the taps and returns the combined output optical signal to the input signal or the signal being processed, and multiplies the optical signals distributed to each tap by an arbitrary weighting coefficient. A coherent signal processing device characterized by signal addition and feedback.