JPH05273443A - Star type optical wiring circuit - Google Patents

Abstract

PURPOSE:To equally distribute a clock signal of small size and send and receive signals among respective LSIs by inputting a light signal which contains the clock signal from right below a conic groove and inputting it to a core. CONSTITUTION:This circuit is provided with a function which superposes the clock signal on the light signal with wavelength lambda1, transmits it from an optical transmission part 9, and equally distributes the signal to respective transmitting receiving circuits 1-1-1-8, and the light signal from one optical transmission part 9 is propagated in cores 3-1-3-8 arranged radially around the conic groove 6 at the center part of a circular substrate 2 and led to respective receiving circuits 1-1-1-8. The light signal with the wavelength lambda1 which is converged in an optical waveguide 7 provided right below the conic groove 6 reaches the comic groove 6 through a 1st clad 4 and is totally reflected and radially diverged, and made equally incident on and coupled with the respective cores 3-1-3-8. The light signals are propagated in the respective cores 3-1-3-8 as shown by arrows 12-1-12-8 and made incident on the respective optical receiving circuits 1-1-1-8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to each LSI utilizing light.
The present invention relates to a star type optical wiring circuit for distributing a clock signal to and from the LSI and for exchanging signals between LSIs.

[0002]

2. Description of the Related Art Recently, high speed of light, low crosstalk,
Studies have been attracting attention for exchanging information signals between rooms, between racks, between boards, between LSIs, and further within an LSI by utilizing the blocking property and non-inductive property of a DC potential.
As an example, a method of distributing a clock signal to each LSI arranged in a distributed manner is proposed, and a main method is (a) a method of distributing an optical signal containing a clock signal by an optical fiber,
There are (b) a method of distributing with a waveguide type coupler, (c) a method of expanding and distributing an optical signal with a lens, and (d) a method of using a hologram (see FIG. 3).

[0003]

However, it is difficult to miniaturize the device or circuit for realizing the various clock distribution systems proposed hitherto, and not only the size and size increase as the number of distribution increases, but also There is a problem that it is difficult to evenly distribute the optical signal.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, to make a compact size, to evenly distribute a clock signal, and to realize the exchange of signals between each LSI. To provide.

[0005]

The star type optical wiring circuit of the present invention, which was conceived to achieve the above object, is roughly divided into the following two modes according to its function.

The first aspect is to provide a function of distributing a clock signal to a plurality of optical receiving circuits (LSIs having a built-in light receiving element) evenly and without delay time variations, in a clad layer on a substrate. Radially formed light propagation core,
An optical receiving circuit is provided at each of the radiating tips of the radially formed cores, and a conical groove is provided at the radiating starting point, and an optical signal including a clock signal is input from directly below the conical groove so that the core It is designed to be combined with.

The second aspect is an LSI in addition to the clock signal distribution function of the star type optical wiring circuit of the first aspect.
In order to have the function of exchanging information signals between the two, a light propagation core is radially formed in the clad layer on the substrate, and a bifurcated optical branching portion is provided at each radiation tip of the radially formed core. And a conical groove is formed at the radiation starting point, a light receiving circuit is connected to one end of the light branching portion, and a light transmitting circuit (part of an LSI containing a light emitting element is connected to the other end). ) Is connected and an optical signal including a clock signal is input from directly under the conical groove to be coupled into the core.

In these embodiments, the cone angle of the conical groove is in the range of 70 ° to 95 °, and directly below the conical groove,
A rod-shaped optical waveguide whose input tip is spherically processed is provided. The core may be radially formed in four or more directions and in multiple directions. It is desirable that the core has a substantially rectangular cross section or a substantially circular cross section, and that the transmission path lengths are equal to each other. Particularly in the second aspect, an interference film filter having a function of transmitting an input optical signal and reflecting a transmission optical signal from the optical transmission circuit is formed on the tip spherical surface of the rod-shaped optical waveguide. Is desirable.

[0009]

When an optical signal including a clock signal is made to enter the star type optical wiring circuit of the first aspect from directly below the conical groove, the incident optical signal is totally reflected by the conical surface of the conical groove and spreads radially. , Is uniformly incident on and coupled to each of the radially formed cores. Since this incident optical signal is coupled to each core at the same time, the clock signal is evenly distributed to the optical receiving circuit connected to the radiation tip of each core without variation in delay time.

Even in the star type optical wiring circuit of the second aspect, the distribution of the clock signal to the optical receiving circuit is realized uniformly and without delay time variation. In this star-type optical wiring circuit, since the optical receiving circuit and the optical transmitting circuit are provided at the respective radiation tips of the core via the bifurcated optical branching portions, the optical signal including the information signal from each optical transmitting circuit is provided. Information signals can be exchanged between the respective LSIs by transmitting the signals. In this case, if an interference film filter having a function of transmitting an input optical signal and reflecting a transmission optical signal from the optical transmission circuit is formed on the tip spherical surface of the rod-shaped optical waveguide, each optical transmission can be performed. Since the optical signal sent from the circuit can be reflected by the conical surface of the conical groove, reflected by the interference film filter, and then reflected again by the conical surface of the conical groove, it can be incident on and coupled to each core. A complete intercommunication circuit network between LSIs is constructed only by this star type optical wiring circuit.

Since the star type optical wiring circuit of the present invention has a waveguide structure, it can be precisely manufactured by using a fine processing technique such as photolithography or dry etching established as a manufacturing technique of a semiconductor integrated circuit. Even if the number of distributions increases, it can be realized in a small size.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

The star type optical wiring circuit shown in FIG. 1 transmits a clock signal on an optical signal having a wavelength λ ₁ from an optical transmitting section 9, and transmits each optical receiving circuit (L having a light receiving element incorporated therein).
SI) is provided with a function of evenly distributing to 1-1 to 1-8, and an optical signal from one optical transmitter 9 is transmitted to the circular substrate 2
Each of the receiving circuits 1-1 propagates through the plurality of cores 3-1 to 3-8 radially arranged with the conical groove 6 at the center as a starting point.
It is designed to lead to ~ 1-8.

The substrate 2 is made of a semiconductor material such as Si, GaAs, InP, SiO ₂ , and a dopant for controlling the refractive index (B, P, Ti, Ge, Al, Zn, Ta, Na, L).
(i, K, etc.), a glass material such as SiO ₂ containing at least one kind, a dielectric material such as LiNbO ₃ , LiTaO ₃ , and a magnetic material are used. A first clad 4 (refractive index n _c1 ) is formed on the substrate 2 so as to cover the surface thereof. As the material of the first clad 4, the same material as that of the substrate 2 can be used. First
The thickness of the clad 4 is selected from the range of several μm to several tens of μm. The core 3-1-3-8 (refractive index _{n w; n w> n c1} )
Are radially formed on the surface of the first cladding 4 starting from the center of the substrate. The cores 3-1 to 3-8 are formed to have a substantially rectangular cross section or a substantially circular cross section, and the same material as the first clad 4 can be used as the material thereof. The thickness and width of the cores 3-1 to 3-8 are selected from the range of several μm to several tens of μm in the case of single mode transmission, and the range of ten and several μm to several hundreds of μm in the case of multimode transmission. Be done. Also,
The relative refractive index difference Δ (= (n _w −n _c1 ) / n _w × 100%) between the refractive index n _w of the cores 3-1 to 3-8 and the first cladding 4 is
In the case of single mode transmission, the range from 0.1% to several%,
In case of multi-mode transmission, 0. It is selected from the range of several% to 10%. The surfaces of these cores 3-1 to 3-8 are covered with the second cladding 5 (refractive index n _c2 ; n _c2 ≈n _c1 ). The conical groove 6 is carved from the surface of the second clad 5 at the radiation starting point of the cores 3-1 to 3-8, and the bottom (conical top) of the groove is formed on the surface of the first clad 4. Has reached The cone angle 2θ of the conical groove 6 is selected from the range of 70 ° to 95 ° in consideration of the propagation loss of the TE and TM modes. The same material as the first clad 4 can be used as the material of the second clad 5, and the thickness thereof is selected similarly to the thickness of the first clad 4. Directly below the conical groove 6 is the substrate 2
And a rod-shaped optical waveguide 7 is provided.
The rod-shaped optical waveguide 7 is provided coaxially with the conical axis of the conical groove 6, and its tip is spherically processed so that an optical signal of wavelength λ ₁ from the optical transmitter 9 can be efficiently condensed. ing. The light receiving circuits 1-1 to 1-8 are arranged on the first cladding 4 so as to be connected to the tip surfaces of the radially formed cores 3-1 to 3-8. The optical signal of wavelength λ ₁ condensed in the optical waveguide 7 reaches the conical groove 6 through the first cladding 4, where it is totally reflected and radially spreads, and the respective cores 3-1 to 3-8. Are evenly incident on and coupled to. The optical signals are directed to the cores 3-1 to 3-8 in the directions of arrows 12-1 to 12-8.
The light propagates inside and enters the respective light receiving circuits 1-1 to 1-8. In order to efficiently propagate the optical signal of wavelength λ ₁ condensed in the rod-shaped optical waveguide 7 into the respective cores 3-1 to 3-8, the number of radially formed cores, that is, the number of distributions. The higher the number, the better. In this embodiment, an example in which the number of cores is 8 is shown, but it may be about 100 or more. The material of the rod-shaped optical waveguide 7 is the core 3
In addition to the same material as that of -1 to 3-8, a material having a higher refractive index (for example, sapphire, ruby, etc.) may be used in order to enhance the optical coupling efficiency with the optical transmitter 9. The distance from the conical groove 6 to each of the light receiving circuits 1-1 to 1-8 is
In order to minimize the delay time of the clock signal, it is desirable that the distance is as equal as possible. In this respect, the star type optical wiring circuit of the present invention uses the precision processing technique similar to the manufacturing technique of the semiconductor integrated circuit. Has an extremely advantageous feature that they can be set equally. Although the substrate 2 is illustrated as having a circular shape in this embodiment, the substrate shape is not limited to this. For example, a rectangle,
It may be oval or the like. In addition, the optical receiving circuits 1-1 to 1-8 are
Other than the LSI having the light receiving element built therein, various electric circuits having the light receiving element built therein may be used. Further, although not shown, it goes without saying that they may include a cooling mechanism, a power supply circuit, various drive circuits, or an electric wiring pattern. Further, instead of the rod-shaped optical waveguide 7, at least one optical coupling system such as a converging rod lens or a spherical lens is used, and an optical signal from the optical transmitter 9 is supplied to each of the cores 3-1 to 3-3. You may make it couple | bond together in 8.

The star type optical wiring circuit shown in FIG. 2 has an LSI in addition to the clock signal distribution function of the optical wiring circuit of FIG.
It also has a function of exchanging information signals between the two, and the light propagation cores 3 radially formed on the substrate 2
Waveguide type bifurcated optical branching devices 11-1 to 11-8 are formed at the respective radiation tips of the optical branching devices 11-1 to 3-8.
To 11-8, optical receiving circuits 1-1 to 1-8 are provided at one end, and optical transmitting circuits (partial circuits of an LSI having a light emitting element) 10-1 to 10-8 at the other end. Are connected. The optical signal of wavelength λ ₁ from the optical transmitter 9 is transmitted as it is to the tip spherical surface of the rod-shaped optical waveguide 7 provided right below the conical groove 6, and the optical signal is transmitted from the optical transmitter circuits 10-1 to 10-8. Wavelength of λ ₂ (≠ λ
An interference film filter 8 for reflecting the optical signal of ₁ ) is coated. Therefore, the distribution of the clock signal is
Similar to FIG. 1, the optical signal of wavelength λ ₁ from the optical transmitter 9 is propagated through the rod-shaped optical waveguide 7 into the respective cores 3-1 to 3-8, and the respective optical receiving circuits 1-1 to Achieved by receiving at 1-8.

The second function of this optical wiring circuit, the LSI
The bidirectional information transmission function between the two is achieved as follows. For example, the information signal from the optical transmission circuit 10-1 is transmitted by being carried on an optical signal of wavelength λ ₂ , and the optical splitter 11-1
Is coupled into the core 3-1 by and propagates toward the conical groove 6. Then, the optical signal is reflected by the conical surface of the conical groove 6, enters the rod-shaped optical waveguide 7, and reaches the interference film filter 8 formed on the spherical portion of the optical waveguide 7. Interference film filter 8
Since it has the property of reflecting the optical signal of the wavelength lambda _2, the wavelength lambda ₂ of the optical signal sent from the optical transmitting circuit 10-1 back is reflected here. Then, the returned optical signal is reflected again by the conical surface of the conical groove 6 and spreads radially, is uniformly incident on the cores 3-1 to 3-8, and is incident on the respective optical branching devices 11-1 to 11-8. Reach Each optical splitter 11
-1 to 11-8 part of the optical signals incident on the optical receiving circuits 1-1 to 1-8 are received, and the remaining optical signals are transmitted to the respective optical transmitting circuits 10-1 to 10-8. Sent. Since the branching ratios of the optical branching devices 11-1 to 11-8 can be set arbitrarily, for example, the coupling amount of the optical signal of the wavelength λ ₂ from the optical transmitting circuit 10-1 to the optical receiving circuit 1-1 side is small. By setting the coupling amount of the optical signal of wavelength λ ₁ from the optical transmitter 9 to the optical receiving circuit 1-1 side to be large, the receiving sensitivity can be increased.

In the configuration of FIG. 2, the oscillation wavelengths of the light emitting elements forming the respective optical transmission circuits 10-1 to 10-8 are made slightly different from each other so that the optical transmission circuits 10-1 to 10-8 respectively have dedicated wavelengths. , Λ ₂₁ , λ ₂₂ , ... λ ₂₇ , λ ₂₈
The optical signal may be transmitted. In this way, each of the optical receiving circuits 1-1 to 1-8 can determine from which optical transmitting circuit 10-1 to 10-8 the optical signal is sent, and the crosstalk can be performed. It is also possible to improve the characteristics. In this case, an optical wavelength tuner is built in each of the optical receiving circuits 1-1 to 1-8, and the optical signal from each of the optical transmitting circuits 10-1 to 10-8 can be discriminated and received by tuning. can do.

In the configuration of FIG. 2, the optical receiving circuit 1
-A light emitting element that emits an optical signal of wavelength λ ₂ is connected after the light receiving element of -1 to 1-8, and the optical signal from the light emitting element is passed through the light receiving element to enter the cores 3-1 to 3-8. If it is sent out, the optical branching devices 11-1 to 11-8 do not have to be used, and the configuration can be extremely simple.

[0019]

In summary, the star type optical wiring circuit of the present invention can exhibit the following excellent effects.

(1) Since the optical signal including the clock signal can be reflected radially by the conical surface of the conical groove and can be evenly and simultaneously coupled into each of the radially formed cores, the radiating tip of the core To the optical receiver circuit connected to the
The clock signal can be distributed without variations in delay time.

(2) In addition to the distribution of the clock signal, the configuration is such that the optical receiving circuit and the optical transmitting circuit are provided at the radiating tip of each of the radially formed cores through the bifurcated optical branching section. It is also possible to send and receive information signals.

(3) Since the waveguide portion consisting of the core, the clad and the conical groove can be precisely formed on the substrate by the fine processing technology established as the manufacturing technology of the semiconductor integrated circuit, the distribution number increases. Can be realized with a small size.

[Brief description of drawings]

1A and 1B are diagrams showing an embodiment of a star type optical wiring circuit according to the present invention, in which FIG. 1A is a plan view and FIG. 1B is a sectional view taken along line AA of FIG.

2A and 2B are views showing another embodiment of the star type optical wiring circuit according to the present invention, wherein FIG. 2A is a plan view and FIG. 2B is AA of FIG.
FIG.

FIG. 3 is a schematic diagram of a conventional clock distribution system using light.

[Explanation of symbols]

 1-1 to 1-8 Optical receiver circuit 2 Substrate 3-1 to 3-8 Core 4 First clad 5 Second clad 6 Conical groove 7 Rod-shaped optical waveguide 8 Interference film filter 9 Optical transmitter 10-1 to 10 -8 Optical transmitter circuit 11-1 to 11-8 Optical branching device

Claims (8)

[Claims] 1. A light propagating core is radially formed in a clad layer on a substrate, an optical receiving circuit is connected to a radiating tip end of the core, and a conical groove is provided at a radiating start point to contain a clock signal. A star type optical wiring circuit, characterized in that an optical signal is inputted from directly below the conical groove and coupled into the core. 2. A light-propagating core is radially formed in a clad layer on a substrate, a bifurcated light branching portion is formed at a radiation tip end portion of the core, and a conical groove is provided at a radiation center portion. An optical receiving circuit is connected to one end of the section, an optical transmitting circuit is connected to the other end, and an optical signal including a clock signal is input from directly below the conical groove and coupled into the core. A star-type optical wiring circuit characterized in that 3. A rod-shaped optical waveguide whose input tip is spherically processed is provided directly below the conical groove.
Alternatively, the star type optical wiring circuit described in 2. 4. The star type optical wiring circuit according to claim 1, wherein the conical groove has a cone angle within a range of 70 ° to 95 °. 5. An interference film filter for transmitting an input optical signal and reflecting a transmission optical signal from the optical transmission circuit is formed on the tip spherical surface of the rod-shaped optical waveguide. The star type optical wiring circuit according to claim 2 or 3. 6. The star type optical wiring circuit according to claim 1, wherein the core is radially formed in at least four directions. 7. The core is formed to have a substantially rectangular cross section or a substantially circular cross section.
5. The star type optical wiring circuit according to any one of 1. 8. The star type optical wiring circuit according to claim 1, wherein the cores are formed so that the transmission path lengths are equal to each other.