JPH0720413A - Composite optical circuit - Google Patents

Abstract

PURPOSE:To provide the composite optical circuit having high stability and high performance by adjacently coupling an optical circuit having waveguides for making modulation or filtering to an optical circuit having waveguides for branching or coupling light signals. CONSTITUTION:The light signal inputted through an optical fiber 11 is branched by the optical branching circuit 12 to 8 pieces of the waveguides and the branched signals are introduced to a Fabry-Perot resonator array 13. At this time, the multilayered films 14, 15 of high-reflectivity dielectrics are deposited by evaporation at both ends of the Fabry-Perot resonator array in such a manner that the refractive index of lithium niobate attains desired reflectivity with respect to the refractive index of quartz glass. The first circuit 12 and the second circuit 13 are joined by optical adhesives 17, 18. Impressed voltages are applied to electrodes 19 added in the Fabry-Perot resonator array to change the refractive indices of the waveguides by an electro-optical effect, by which the filtering is executed. The filtered light signals are taken out of a fiber array 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite optical circuit, and more particularly to a composite optical circuit in which modulators, switches and filters for optical communication or optical measurement are two-dimensionally distributed to form a small optical component. It relates to an optical circuit.

[0002]

2. Description of the Related Art FIG. 3 is a diagram for explaining a conventional optical circuit having a single structure. For example, a waveguide portion having a high refractive index is partially formed on a quartz substrate 1. An optical circuit is formed by forming an optical coupler, a ring interferometer, or a combination thereof. Reference numerals 2 and 6 are optical fibers, 3 is an optical branching portion, 4 is a resonator portion, and 5 is an electrode.

The optical signal propagating through the optical fiber 2 is branched by the optical branching section 3, filtered by the resonator section 4, and the filtered signal is taken out from the optical fiber 6. The adjustment of the filtering is realized by subtly changing the apparent waveguide length by the electric power applied to the resonator section through the electrode 5.

[0004]

However, since such a conventional optical circuit uses a glass-based material such as quartz, the operating speed for filtering or the like is such that the electrode is used as a heater and the refractive index of the waveguide is changed. Since it uses temperature change, it is limited to several tens of ms at most.

On the other hand, in an optical circuit using a semiconductor material such as lithium niobate or GaAs, the response speed can be increased, but when the bend of the waveguide becomes large, the waveguide loss rapidly increases. There was a problem that circuits could only be formed to a certain degree.

Further, the size of the substrate that can be used is only smaller than that of glass such as quartz, and there is a problem that a large circuit cannot be formed. Therefore, only a circuit in which a simple waveguide structure such as a normal Y branch is combined can be realized.

The present invention has been made to solve the above problems, and an object of the present invention is to enable high speed operation.
Moreover, it is to provide an optical circuit capable of simultaneously handling a plurality of eight or more waveguides.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[0009]

In order to achieve the above object, the composite optical circuit of the present invention modulates the optical signal at high speed on a first optical circuit having a waveguide for branching or coupling the optical signal. Or a second having a filtering waveguide
The main feature is that the optical circuits of (1) and (2) are joined adjacently via the refractive index adjusting region.

In the composite optical circuit, a silica-based waveguide type optical circuit is used as the first optical circuit.

In the above composite optical circuit, a lithium niobate waveguide type optical circuit is used as the second optical circuit.

[0012]

According to the above-mentioned means, the first optical circuit for branching or coupling the optical signals, which has a large bending, such as a quartz system, which has a small bending loss, is used for the circuit section for modulating or filtering the optical signals at a high speed. Lithium niobate and Ga
Since the second optical circuit formed of a semiconductor material such as As is joined and integrated, it has not been possible until now.
It is possible to obtain a highly stable and high-performance composite optical circuit.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the composite optical circuit of the present invention. In this embodiment, as shown in FIG. 1, an optical fiber 11, an optical branch circuit 12 made of a silica-based material as a first optical circuit, and a Fabry-Perot resonance made of lithium niobate as a second optical circuit. Device array 13, high-reflection dielectric multilayer film 1 deposited on both ends thereof
4, 15, optical fiber array 16, optical adhesives 17, 18 for joining the first optical circuit and the second optical circuit,
It is composed of electrodes 19 for operating the Fabry-Perot resonator.

In the structure of the composite optical circuit shown in FIG. 1, the optical signal inputted through the optical fiber 11 is the optical branch circuit 12
Is demultiplexed into eight waveguides and guided to the Fabry-Perot resonator array 13. At this time, highly reflective dielectric multilayer films 14 and 15 are vapor-deposited on both ends of the Fabry-Perot resonator so that the refractive index of lithium niobate becomes a desired reflectance with respect to the refractive index of quartz glass. When a modulator array or the like is mounted instead of the Fabry-Perot resonator, a non-reflective dielectric multilayer film is vapor-deposited on silica glass so that there is no reflection due to the refractive index of lithium niobate.

The first circuit 12 and the second circuit 13 are joined by optical adhesives 17 and 18. Optical adhesive 17,1
The refractive index of 8 was the same as that of quartz glass. The gap between the waveguide arrays on the joint surface between the first circuit 12 and the second circuit 13 is unified to 250 μm, and the eight waveguides are connected with a variation of 2-3 dB or less.

Electro-optic (EO) is performed by applying an applied voltage to the electrode 19 added in the Fabry-Perot resonator.
The effect changes the refractive index of the waveguide and filters. The filtered optical signal was extracted from the fiber array 16.

FIG. 2 shows that the wavelength of the input optical signal is 1.536 μm.
The optical frequency of the semiconductor laser is swept and the output optical signal of each waveguide is observed. The average excess loss at each connection point was about 1 dB, and almost uniform Fabry-Perot resonance characteristics were obtained for all the waveguides.

It was also confirmed that the resonance peak can be varied by applying an electric field through the electrodes, and the operation as an optical filter was also confirmed.

In the case where the circuit of FIG. 1 is entirely made of lithium niobate, the output light signal is below the detection limit because the loss at the branch is large, and the resonance characteristic cannot be observed.

In this embodiment, an example using quartz glass as the first optical circuit and lithium niobate as the second optical circuit is shown. However, lithium tantalate, potassium niobate,
Dielectric crystals such as KDP, semiconductor materials such as GaAs and InGaAs, POM, NPP, AANP, DAN,
The same effect can be obtained by using an organic crystal material such as DMNP or an EO (electro-optical) polymer material obtained by polarization treatment of PMMA or the like which binds an azo dye or a stilbene dye.

Although the present invention has been specifically described based on the embodiments, it is needless to say that the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Absent.

[0023]

As described above, according to the present invention, a silica-based waveguide suitable for a waveguide for branching or coupling an optical signal is used as the first optical circuit and the optical signal is modulated at high speed. A waveguide formed of a dielectric crystal such as lithium niobate suitable for filtering, a semiconductor such as GaAs, or an EO polymer material is used as a second optical circuit, and both are joined by an optical adhesive whose refractive index is adjusted. By taking advantage of the advantages of (1), it is possible to obtain an extremely high-stability, high-performance composite optical circuit that could not be achieved until now.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a composite optical circuit of the present invention,

FIG. 2 is a block diagram showing an example of measurement of optical characteristics when a 1 × 8 optical coupler and a Fabry-Perot resonator are configured as the composite optical circuit of the present embodiment,

FIG. 3 is a diagram showing a conventional optical circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical circuit, 2, 6, 11 ... Optical fiber, 3, 12 ... Optical branch circuit, 4 ... Ring resonator, 5 ... Electrode, 13 ... Fabry-Perot resonator array, 14, 15 ... Dielectric multilayer film, 16
... optical fiber array, 17, 18 ... optical adhesive.

Claims (3)

[Claims] 1. A first optical circuit having a waveguide for branching or coupling an optical signal, and a second optical circuit having a waveguide for modulating or filtering the optical signal at high speed,
A composite optical circuit characterized in that they are adjacently bonded to each other via a refractive index adjusting region. 2. The composite optical circuit according to claim 1,
A composite optical circuit, characterized in that a silica-based waveguide type optical circuit is used as the first optical circuit. 3. The composite optical circuit according to claim 1, wherein a lithium niobate waveguide type optical circuit is used as the second optical circuit.