JPS58142320A - Waveguide type optical switch - Google Patents

Abstract

PURPOSE:To improve an extinction ratio by forming a thin film-like lens which converges input light toward an electrode pair on optical waveguides. CONSTITUTION:Two crossing optical waveguides 32-1, 32-2 are formed within the surface layer of a ferrodielectric crystal 33, and a pair of electrodes 34, 34' like flat plates are provided at the crossing part. A thin film-like lens 31 is provided the position where input light P converges toward the electrodes 34, 34'. The relation n2>n1>n3 is required to produce a lens effect if the refractive index of the lens 31 is defined as n1, the refractive index of the waveguide 32-1 as n2 and the refractive index of the crystal 33 as n3. Part of the input light P is sucked up into the lens 31 from the waveguide 32-1, receives the convergent effect of (n2>n1) of the lens and returns again into the original waveguide 32-1. The relation n1>n2 is required to confine the light particularly in the waveguide 32-1 in the crystal 33.

Description

[Detailed description of the invention] (1) Technical field of the invention Misfiring #i relates to a waveguide type optical switch.

(2) Background of the technology In recent years, there has been an increase in the number of platforms that use light as a transmission medium for communication systems. This is because the original signal exhibits better communication characteristics than the original signal. With the expansion of such optical communication systems, ea+x devices have been proposed and improved. Among these various devices, the unfired aA is particularly contradictory to the waveguide type optical switch.

(3) Prior art and melting point FIG. 1 is a plan view showing the basic configuration of a general waveguide type optical switch. In this case, reference numeral 11fl indicates seven optical eyelets, and a waveguide type optical switch 10 is inserted between these optical seven eyeers 11. Original switch 1O
fl'l [The brocade crystal is made of lithium niobate, and has two optical waveguides 12-1 and 12- in its surface layer.
2 are formed by crossing each other. For example, it is formed by diffusion of titanium. Furthermore, a flat electrode pair 14 and 14' is arranged at the intersection.

Now, assuming that the input source P is irradiated so as to melt water, the #input light P passes through the path pipe of original fiber 11" (lower left) → optical waveguide 12-1 → optical fiber 11 (upper right) and outputs light P. On this platform, no voltage <V> is applied to the electrode pair 14, 14', and the electric field between them is zero. However, a voltage (V) is applied to the electrode pair 14, 14'.
) to create an electric field between them, now F
In IL, the input light P is connected to a single fiber 11 (bottom left) →
Optical waveguide 12-1 → Optical waveguide 12-2 → Optical 7 Eyeper 1
Output light P passes through path 1 (bottom right). get. Here is the output light P. represents the light that passes through one switch, and the output light P. is switched with a switch and nine yt,
represents. To give a good example of the use of such an original switch, if the address signal on the inputs Jjt and P is detected by the output light ~, and the address belongs to the main switch,
Operate the switch to convert input light P to output light P. The optical signal t switch can be guided to the electronic exchange 1sfI1.
can be replaced.

The optical switch shown in 1rkJ still has many points to be improved. In the present invention, attention is paid to the extinction ratio of 1% among the points to be improved. In other words, with the conventional original switch, it was not possible to find a sufficiently large extinction ratio, and there was a need for improvement in terms of performance as an optical switch.

Figure @2 is a graph to clarify the extinction ratio 91r of a waveguide type optical switch. In this graph, the mechanical axis shows the voltage applied to the electrode pair 14, 14' (11th), and the vertical axis shows the output light ~2. Take the output power PWt of ~.

sw on the horizontal axis indicates the switching time of the optical switch.

Book 27 Monkey symbol P. onn through mode 0 cutoff
-Representation"(,1off represents the output power when the through mode is stopped. Also, the symbol P.7. is the output power when the switch mode is stopped. %!J
on' %)o represents the output flow in switch mode. In this graph, especially the dotted curve y. onIa, regarding the conventional characteristics, the solid line is CAR2. This is a characteristic related to the present invention for the n-line, which will be described later. The extinction ratio is, for example, 12.6 dB per 1iI of the output power in this graph.

In the graph shown in No. 211, the switching efficiency is poor with the conventional characteristics (dotted line curve), and the level difference t-R
It is desired to improve the extinction ratio by increasing the extinction ratio from ' to RC).

(4) Object of the Invention The object of the present invention is to solve the problem of the above-mentioned poor extinction ratio and to propose a waveguide type optical switch that can significantly improve the extinction ratio by 11 gJ.

(5) Structure of the Invention The above object is achieved by configuring a light-focusing type film-like lens on an optical waveguide so that an input source is focused toward a pair of electrodes.

(6) Examples of the invention Embodiments of the present invention will be described below with reference to the drawings.

Figure 3 shows Ichikyo &! based on the present invention. This is a perspective view showing Example I. In this book, reference number 31 is a feature of the present invention.
Thin film-like lens, light focusing type.

For other configurations, please feel free to ask me if you have any questions. .

That is, the number reference number 33 is a gk adielectric crystal, and the surface of is formed.At the intersection, a turtle on a flat plate &#a4,
34'(1-14.14') is provided.
.

Lens 31 frame - swivels to the position shown. The position lit is such that the input source P is focused towards the electrode pair 34 and 34'.

By giving a lens effect like this.

The intended purpose is achieved. If you show it with a trial example, the above @2
In the graph shown in the figure, go to the actual curve. . As shown in To
As a result, the level difference increases from the conventional R' to R. Expressed numerically, the extinction ratio is from 12.6 dB to 15.5 dB.
be lifted up. However, the theoretical static axis as to how the extinction ratio is improved by adding such a lens effect is not clear at this stage. In any case, the extinction ratio can be increased by forming such a lens on the optical waveguide of the device.

In order to produce the above-mentioned lens effect, simply providing the lens 31 is insufficient; however, the refractive index KIII is insufficient.
Certain conditions are required. This will be explained with reference to Figure t-5tt4. Figure i84 is a 2-in 4-4 section FB- of Figure Rin3. Here, the refractive index t of the lens 31
The refractive index of the nl s optical waveguide 32-1 [nss, where nl is that of the ferroelectric crystal 33, is set to the relationship ns>nl>ns. Then, as shown by the arrow in Figure ii4, a part of the input light P is sucked up from the optical waveguide 32-1 into the lens 31 (nl>nl), and is returned to the original optical waveguide 32 after receiving the focusing action of the lens. - Return to 1 yen. Note that in order to confine light particularly in the optical waveguide 32-1 within the one-strong electrolyte crystal 33, a nt>nso coupling is required.

(7) As described in detail, according to the present invention, the extinction ratio is equal to wJ
The waveguide-shaped nine crosses that are served by the attendant are drowning in pain.

[Brief explanation of the drawing]

Figure 1 shows the i-ellipse formation of a general waveguide chromatic switch, and @2&J shows Gun 7. Figure 3 is a perspective view showing one embodiment of the present invention, and Figure 4 is a cross section taken at 2-in 4-4 in Figure 1143. 31...III-shaped lens, 32-1.32-2.
・Optical waveguide, 33...strongly fermented turtle crystal, 34.34'・
...lIE&vs. Patent applicant Fujitsu Ltd. Patent application agent Akira Shioiri, patent attorney Patent attorney Akira Aoki Illustrations Kazuyuki Tate Patent attorney 1) Yukio Patent attorney Akira Yamaguchi (Figure 1, Figure 2) W v →

Claims (1)

[Claims] 1. Two optical waveguides formed to intersect within the surface layer of a ferroelectric crystal, and a pair of flat electrodes that selectively form an electric field at the intersection Os. # Switches the optical path of light propagating through the optical waveguide from one wrinkle-guided waveguide to the other optical waveguide depending on the presence or absence of an electric field, or prevents the wrinkle-guided waveguide from switching. , a light-focusing thin film lens is formed on the surface WJIIi of the ferroelectric crystal, the thin film lens is disposed at a position where the light passing through the lens is focused on the electrode pair; A waveguide shape characterized in that, assuming that the refractive indices of the shaped lens, the optical wave path, and the ferroelectric crystal are respectively n1*nff1 and phantom, the relationship between them is set to ns>nt>nru. light switch.