JPS6364006A - Integrated optical filter - Google Patents

Abstract

PURPOSE:To enable non-contact and exact detection of the temp. fluctuation in optical filters as light information by forming the two optical filters on the same substrate by using two kinds of materials having the different temp. coeffts. of refractive index. CONSTITUTION:The optical filters F1, F2 are formed by using the ring interferometers of the same shape and waveguides 5, 8, 9 (or 6, 10) are formed by using InP (or GaAs), on the substrate 7. A directional coupler 1 couples input light Pi to the filters F1, F2 and a coupler 2 bisects the output light P01 from the filter F1. Couplers 3, 4 branch the light advancing in linear waveguides 9, 10 to ring type waveguides 5, 6. The input light Pi; for example, 1.55mum light, is split to 2:1 by the coupler 1 and is branched to the filters F1, F2; further, the output light P01 is bisected by the coupler 2, when said light is inputted to this element. The respective temp. coeffts. of the refractive index of InP and GaAs move by 84MHz and 127MHz to the low-frequency side if it is assumed that the temp. of the element rises by 0.01 deg.C. The temp. fluctuation quantity is, therefore, obtd. by detecting the same.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an integrated optical filter that can provide information on its own temperature variation to the output intensity from the optical filter.

[Conventional technology] In order to detect temperature fluctuations in the filter characteristics of an optical filter, conventional technology uses thermal lightning pairs, thermistors, etc. as sensors and brings them into direct contact with the optical filter. It was necessary to read the temperature fluctuations.

An optical filter is a component whose light transmittance is determined according to the optical frequency of input light.

[Problems to be solved by the invention] However, in this method, since the sensor has a certain size, it is difficult to say that it accurately measures the temperature of the minute optical filter itself, and it is difficult to say that the temperature of the tiny optical filter itself is measured accurately. It was not possible to detect any temperature fluctuations inside the optical filter that controls this.

An object of the present invention is to provide an integrated optical filter having a structure that allows non-contact and accurate detection of temperature fluctuations inside an optical filter, which control minute filter characteristics of the optical filter, as optical information.

[Means for Solving the Problems] The present invention is composed of two optical filters each having a waveguide structure using two types of materials having different refractive index iin power coefficients, and the output from the two optical filters is This is characterized in that temperature fluctuations in the optical filter can be detected from fluctuations in intensity.

[Function] The present invention uses the above means to read and compare variations in the output light intensity from two optical filters due to temperature variations, thereby detecting temperature variations in the optical filters. It is possible to accurately detect QR degree fluctuations inside the optical filter, which controls the characteristics, as optical information in a non-contact manner.

[Example code] Embodiments of the present invention will be described in detail below with reference to the drawings.

(Example 1) FIG. 1 is a diagram explaining the first example of the present invention,
Solid lines indicate waveguides. The thin wires 5, 8.9 are made of I as a material.
A waveguide using nP and a thick line 6°10 indicate a waveguide using GaAs material. These are all manufactured on the same substrate 7. The dotted arrows in the figure indicate optical input Pl, optical output O,
,02°03. In this embodiment, ring interferometers are used as the optical filters F1 and F2. 1 is a directional coupler for splitting input light into two optical filters PL and F2, and 2 is a directional coupler for splitting output light from optical filter F1 into two lights.

3.4 represents a directional coupler that splits the light traveling through the straight waveguides 9 and 10 into the ring waveguides 5 and 6, respectively. The optical filters F, , F2 have the same shape and size. By configuring the optical filters F, , F2 on the same substrate 7, they can constitute one element. Light output O1
is used for measurement as light that has passed through the optical filter F1, as in the prior art. Light output o2. o3 is monitored by a light receiver. FIG. 2 shows the filter characteristics of the optical filter F1, and FIG. 3 shows the filter characteristics of the optical filter F2.

The frequency transmission characteristics are different between FIG. 2 and FIG. 3 (here, the period is different).

Now, consider the case where light of 1.55 μm (the position of the arrow in FIGS. 2 and 3) is input to this element as the optical input Pi. This human power light is divided 2:1 by the directional coupler 1 and input to the optical filters F, , F2.

Let this input light intensity be Pfl and Pi2. In other words, the output light intensity from optical filters F1 and F2 is POI, PO2
Then, from Figures 2 and 3 (from the intersection of the characteristic curve and the arrow) Pc 1'=0.168P1 t=O, 112
P t, Po 2-0.230 P 12-0.0
It can be seen that the value is 77PI. The subsequent output is shown in FIG.

The directional coupler 2 divides the POI into two equal parts, pol 1-0.
5 P, ) , -0,084P i 1-0.058
Pi.

Po 12 mo, 5 POH-0,084P i H
-0,058Pi.

Consider a case where the temperature of this element increases by O,Ol''C.

Temperature coefficient of refractive index of InP Δn −1,3756X 1
0-'/, the temperature coefficient Δn-2 of the refractive index of GaAs
, 2124
2. As shown in FIG. 5, o3 is P(, 12=
0.090 Pi 1-0.060 Pl, P(,
2=0.251 P i 2-0.084 P i. By detecting this variation, the amount of temperature variation can be determined. Furthermore, since the amount of change in filter characteristics due to temperature differs between the optical filters F, F2, it is possible to detect the amount of temperature change even if the optical frequency of the incident light changes.

This is because the optical frequency fluctuation of the incident light is caused by the optical filter F.
The filter characteristics of F2 fluctuate by the same amount, and the optical output is 0.2. By monitoring the intensity of o3, it is possible to separate the optical output fluctuation due to the optical frequency fluctuation of the human-powered light from the optical output fluctuation due to the temperature fluctuation of the optical filter.

(Example 2) FIG. 6 is a diagram illustrating a second example of the present invention.
The dashed dotted lines represent optical filters Fl and F2. Further, the thin line represents a waveguide using an InP material, and the thick line represents a waveguide using a GaAs material.

1 is a directional coupler for splitting input light into two optical filters, and 2 is a directional coupler for splitting output light from the optical filter F1 into two lights.

The principle is exactly the same as the first embodiment.

(Embodiment 3) FIG. 7 is a diagram for explaining the third embodiment of the present invention, in which F3
F4 represents a Fabry-Perot etalon type optical filter in which high reflection films are formed on both end faces of an InP waveguide, and F4 represents a Fabry-Perot etalon type optical filter using a GaAs waveguide.

Solid lines represent waveguides.

The principle is exactly the same as the first embodiment.

(Example 4) Figure 8 # (a) is a diagram explaining the fourth example of the present invention, where the thin line is a waveguide using InP material No. 4, and the thick line is G
It represents a waveguide using aAs material.

The portion surrounded by the dashed line represents the optical filter F1°F2, and here a grating-type optical filter in which a grating is cut inside the waveguide is used. FIG. 8(b) is an enlarged sectional view of this waveguide grating type optical filter section.

The principle is exactly the same as the first embodiment.

(Embodiment 5) In FIGS. 1, 6, 7, and 8, the present invention can be carried out by using two materials, GaAs and 5102, and forming two optical filters.

The principle is exactly the same as that described in the first embodiment.

(Example 6) In FIG. 1, FIG. 6, FIG. 7, and FIG. 8, the present invention can be carried out by forming two optical filters using two types of materials, InP and 5i02.

The principle is exactly the same as described in the first embodiment.

[Effects of the Invention] As described above, according to the present invention, two optical filters are formed on the same substrate using two types of materials with different temperature coefficients of refractive index, and the output intensity of the two optical filters is By monitoring and comparing the fluctuations, it is possible to detect temperature fluctuations in the optical filter without affecting the fluctuations in the wavelength of the incident light, allowing for non-contact measurement of filter characteristics that could not be measured with conventional technology. This has the advantage of being able to detect temperature fluctuations inside the optical filter.

Although specific examples 1 to 6 have been described, the present invention is not limited to only these examples, and other examples can be made by combining two types of materials with different temperature coefficients of refractive index. Needless to say, it's possible.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing the first embodiment of the present invention, and FIG. 2 is a diagram showing the characteristics of a waveguide type optical filter F1 using the material 1 n P :t in FIG. 1. Figure 3 is the first
Waveguide type optical filter F2 using GaAs material in the figure
FIG. 4 shows the optical output O! of the device shown in FIG. 1 when the optical input P1 is set to 1. , a diagram showing the optical output 02+ and the optical output 03, FIG. 5 shows the temperature of the element 0.01
Light output when increased by °C 01. A diagram showing optical output 02 and optical output 03, FIG. 6 is a configuration explanatory diagram showing the second embodiment of the present invention, and FIGS. 7 and 8 are diagrams showing the third and fourth embodiments of the present invention.
FIG. 2 is a configuration explanatory diagram showing an embodiment of the invention. F, , F2... optical filter, 5. ill, 9...I
Waveguide using nP material, 6.10... Waveguide using GaAs material, 1... Directional coupler for splitting input light into two optical filters, 2... Optical filter A directional coupler that splits the output light from F into two lights, 3.4
... Directional coupler, 5, 6 ... Ring waveguide, 8
, 9...Fabry-Perot filter. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Liquid recording Hz] Figure 2 Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) Consisting of two optical filters with waveguide structures using two types of materials with different temperature coefficients of refractive index,
An integrated optical filter characterized in that temperature fluctuations in the optical filters can be detected from fluctuations in output light intensity from the two optical filters. (2) The integrated optical filter according to claim 1, characterized in that the optical filter is an optical filter that constitutes one element by two optical filters being constructed on the same substrate. (3) As an optical filter, a directional coupler for distributing incident light to two optical filters is configured on the light input side of the optical filter, and a waveguide on the output side of at least one optical filter is configured. Claim 1, characterized in that an optical filter in which a directional coupler is configured is used.
Integrated optical filter as described in Section.