JP2001235716A - Optical-electric mixture substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems of a conventional optical-electric mixture substrate that the temperature difference between the core of the optical waveguide and the temperature detector disposed on the substrate is large and the measurement of the temperature of the optical waveguide with good accuracy is difficult. SOLUTION: A mount for optical parts and electronic parts, an optical waveguide to which optical parts are to be connected, a resistor 12 as a temperature sensor which consists of a metal or semiconductor to detect the temperature of the optical waveguide and which is disposed near under the optical waveguide are formed on a substrate 11. The product (A) of the reciprocal of the thermal conductivity of the optical waveguide and the distance from the center of the core 13 of the optical waveguide to the surface of the substrate 11, and the product (B) of the reciprocal of the thermal conductivity of the substrate 11 and the thickness of the substrate 11 are controlled to satisfy A/B>=19. Since a gentle temperature gradient is generated in the optical waveguide and the temperature difference between the core 13 and the resistor 12 for the temperature sensor is decreased, the temperature of the core 13 of the optical waveguide can be measured and detected with good accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the temperature of an optical waveguide used in an optical communication connection portion between electronic component substrates such as an optical communication system and a computer or an optical signal conversion region between elements in an electronic component substrate. The present invention relates to a required opto-electric mixed board, and more particularly to an opto-electric mixed board with improved temperature detection accuracy of an optical waveguide.

[0002]

2. Description of the Related Art In an optical signal transmission system used in an optical communication system, a computer, an exchange, or the like, a device or material whose characteristics depend on temperature, or an optical / electronic mixed device in which optical components or electronic components utilizing temperature change are mixed. Substrates are often used. For example, among optical components, the threshold current of light emission of a laser diode changes depending on the temperature. In addition, the refractive index and the density of a quartz or organic optical waveguide change depending on the temperature, and there are optical switches and the like that positively use the refractive index and density. As described above, temperature is one of the important factors that affect the characteristics of optical components, so detecting and controlling the temperature of a board with mixed optoelectronics is a necessary technology for stable operation of optical components. It is.

[0003] As an example of a conventional photoelectron mixed substrate provided with a temperature sensor for an optical waveguide, FIG.
2 is a cross-sectional view of an optical delay device using the O effect. In this optical delay device, an optical waveguide substrate 24 on which an optical waveguide 23 is formed is attached to the upper surface of a heat conductive plate 21 via a heat conductive medium 22 such as heat conductive grease, and A temperature control element 25 such as a Peltier element is provided so that the heat conduction plate 21 can be heated and cooled.The temperature of the heat conduction plate 21 is measured by a temperature sensor 26 attached to the heat conduction plate 21, and the temperature is controlled by a temperature control circuit 27. The adjustment is performed.

FIG. 4 is a sectional view of an optical waveguide used in such an optical delay device. In FIG. 4, reference numeral 31 denotes an optical waveguide substrate, on which an optical waveguide composed of a core part 32 and a clad part 33 made of silica or an organic optical material is formed. A heater 34 is provided on the upper surface of the cladding 33.
Are provided in close contact with each other, and the optical waveguide, particularly the core portion 32, is heated by the heater 34 by energization to increase the optical path length of the optical waveguide, thereby causing an optical delay.

[0005] Normally, silicon is generally used for a support substrate of an optical component requiring such temperature control.
This is because silicon has excellent workability of the V-groove, excellent heat resistance, and has a relatively high thermal conductivity, and thus has good heat dissipation. In addition, quartz and organic optical materials are generally used as the material of the optical waveguide as an optical component, and both optical materials have low thermal conductivity.

[0006]

However, in the optical waveguide 23 in which the temperature is detected by the temperature sensor 26 and the temperature is controlled, the portion which affects the delay characteristic of the optical signal is located immediately below the heater 34. In the vicinity of the core portion 32, accurate measurement of the temperature in this range is required for a high-precision optical delay device. On the other hand, the optical waveguide 23 to the optical waveguide substrate 24 and the heat conductive medium as shown in FIG. At the position of the temperature sensor 26 provided on the heat conducting plate 21 via
Since the heat conductivity of the heat conductive plate 24 and the heat conductive plate 21 is good, there is a problem that only an average temperature in these two ranges can be detected.

As a countermeasure, in order to accurately detect the temperature of the optical waveguide, it is conceivable to bring the temperature sensor as close as possible to the optical waveguide where the temperature is to be measured, and the present inventor has disclosed in Japanese Patent Application No. 11-277555. A photo-electron mixed substrate in which the temperature sensing element is arranged close to the optical waveguide was proposed. According to this photoelectron mixed substrate, the measurement accuracy for the temperature of the optical waveguide is considerably improved.

However, even when the temperature detecting element is disposed close to the optical waveguide, the temperature detecting element is 7.5 μm from the center of the core due to the influence of light seeping out from the core of the optical waveguide. The degree needs to be placed at a distance. For this reason, the thermal conductivity of the optical waveguide substrate is good,
If the thermal conductivity of the optical waveguide is poor, the thermal resistance of the optical waveguide substrate becomes smaller than the thermal resistance of the optical waveguide, so that a steep temperature gradient occurs inside the optical waveguide, and the In some cases, the temperature difference between the core portion and the upper surface portion of the optical waveguide substrate on which the temperature detecting element is arranged becomes large, and there is a tendency that the temperature cannot be measured accurately.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a photoelectron mixed device capable of accurately measuring the temperature of an optical waveguide and thereby performing good temperature control of the optical waveguide. It is to provide a substrate.

[0010]

According to the present invention, there is provided an optical / electrical mixed substrate comprising: a mounting portion for an optical component and an electronic component; an optical waveguide to which the optical component is connected; and a part of the optical waveguide. A temperature detecting element made of a metal or a semiconductor for detecting the temperature of the optical waveguide, which is disposed in proximity to the substrate, is formed from the reciprocal of the thermal conductivity of the optical waveguide and the center of the core of the optical waveguide. The product A of the distance to the surface is A / B with the product B of the reciprocal of the thermal conductivity of the substrate and the thickness of the substrate.
≧ 19.

Further, in the electric mixed board of the present invention, in the above structure, the product B of the reciprocal of the thermal conductivity of the board and the thickness of the board is at least 2.85 × 10 ^-4 W ^-1 · m ² · K. It is characterized by the following.

[0012]

According to the photoelectron-mixed substrate of the present invention, the reciprocal of the thermal conductivity of the optical waveguide and the distance from the center of the core portion of the optical waveguide to the surface of the substrate below which the temperature detecting element is disposed are described. Is a predetermined range as described above, that is, A is a product of the product B of the reciprocal of the thermal conductivity of the substrate and the thickness of the substrate.
By setting / B ≧ 19, the thermal resistance of the optical waveguide is relatively smaller than the thermal resistance of the substrate, and the temperature of the upper surface of the substrate is closer to the temperature of the center of the core of the optical waveguide than the temperature of the lower surface of the substrate. Therefore, a gentle temperature gradient is generated inside the optical waveguide, and the temperature difference between the core portion of the optical waveguide and the surface of the substrate on which the temperature detecting element is arranged becomes small, so that the temperature of the optical waveguide can be accurately measured.

When the product B of the reciprocal of the thermal conductivity of the substrate and the thickness of the substrate is set to 2.85 × 10 ⁻⁴ W ⁻¹ · m ² · K or more, an organic material sensitive to the thermo-optic (TO) effect is obtained. Since the above A / B can be set to 19 or more even for the optical waveguide material of the system, a photo-electron mixed substrate that can measure the temperature of the optical waveguide more accurately can be obtained.

Hereinafter, the photoelectric mixed substrate of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an example of an embodiment of a photoelectron-mixed substrate according to the present invention, and FIG. 2 is a sectional view taken along the line AA 'of FIG. In the photoelectric mixed substrate shown in FIGS. 1 and 2, a thin-film temperature sensor resistor 12 which is a temperature detecting element made of metal or semiconductor is formed on a support substrate 11, and a signal light is transmitted thereon. An optical waveguide comprising a core portion 13 and a cladding portion 14 for controlling the temperature, and a temperature control resistor 15 is formed thereon. In this example, switching is performed by changing the optical path length of the core portion 13 of the optical waveguide by the thermo-optic effect.

The optical components, the electronic components, and their mounting portions are not shown.

Here, the portion where the temperature is to be measured and detected by the temperature detecting element is a portion of the optical waveguide located below the temperature control resistor 15, and the temperature detecting element is provided on the substrate 11 therebelow. A temperature sensor resistor 12 is formed close to the optical waveguide. Thereby, the temperature sensor resistor with respect to the temperature is very close to the core 13 which is the object to be measured.
The temperature of the core portion 13 of the optical waveguide can be detected by measuring the change in the resistance value of the optical waveguide 12.

However, there is a certain limit to the proximity of the temperature sensor resistor 12 to the core 13 of the optical waveguide. This is, specifically, unless the distance from the core 13 to the temperature sensor resistor 12 is about 7.5 μm,
The exudation of the optical signal transmitted by the core portion 13 to the cladding portion 14 prevents the temperature sensor resistor 12 made of a metal or the like.
Does not have optically good characteristics, which may result in a significant deterioration in the optical characteristics of the optical waveguide. Thus, the core 13 and the temperature sensor resistor 12
Under a condition that a predetermined distance must be secured between the optical waveguide and the substrate 11, the thermal conductivity of the optical material forming the core portion 13 and the cladding portion 14 is generally smaller than the thermal conductivity of the material of the substrate 11. Temperature, the temperature gradient inside the optical waveguide becomes large, and a temperature difference occurs between the core 13 as the temperature measuring part and the resistor 12 for the temperature sensor, thereby lowering the temperature measurement accuracy. Will do.

Here, for example, in an Mach-Zehnder type optical switch, it is necessary to shift the phase of light by π due to a temperature difference of 4 ° C. at the time of switching. It is necessary to control the amount with an accuracy of 5% or less, which is 0.05π or less.

On the other hand, in the case of an optical waveguide made of a siloxane-based polymer, which is one of the organic optical materials, the change in the optical path length due to temperature is much larger than that of a quartz-based optical waveguide. When a temperature difference of 4 ° C. is applied by heating in the range, a phase shift of about π occurs. Then 0.05
If there is a phase shift of π, the extinction ratio becomes smaller than 20 dB. Therefore, it is necessary to control the temperature within a range of 5%, that is, 0.2 ° C., which is 5%.

The temperature difference between the core portion 13 as the temperature measuring portion and the temperature sensor resistor 12 as the temperature detecting element is determined by the substrate 11
And the thickness and thermal conductivity of each of the optical waveguides have a great influence. When the thickness of the substrate 11 and the optical waveguide is sufficiently small, the direction of heat radiation from the core 13 flows almost directly to the substrate 11 side, so that the temperature difference between the core 13 and the temperature sensor resistor 12 is It is proportional to the thickness and inversely proportional to the thermal conductivity. In order for the error to be 0.2 ° C. or less for a temperature difference of 4 ° C., the product of the reciprocal of thermal conductivity from the center of the core portion 13 of the optical waveguide to the surface (upper surface) of the substrate 11 and the thickness is the core of the optical waveguide It is necessary to be 5% or less of the product of the thickness from the portion 13 to the lower surface of the substrate 11 and the reciprocal of the thermal conductivity.

Here, considering the distance from the center of the core portion 13 of the optical waveguide to the upper surface of the substrate 11, the thermal conductivity of the organic optical waveguide is as high as 0.5 W · m ⁻¹ · K ⁻¹ . When the distance from the core portion 13 to the upper surface of the substrate 11 is the minimum of 7.5 μm, the product A of the thickness of 1.5 × 10 ⁻⁵ W ⁻¹ · m ² · K and the reciprocal of the thermal conductivity is obtained. Therefore, the product of the thickness of the optical waveguide from the core 13 to the lower surface of the substrate 11 and the reciprocal of the thermal conductivity is 3.0 × 10 ⁻⁴ W ⁻¹ ·, which is 20 times the product A of the optical waveguide.
m ² · K or more, the product B of the reciprocal of the thickness and thermal conductivity of the substrate is 19 times the product A of the optical waveguide portion ^{2.85 × 10 -4 W -1 · m} 2
-It must be K or more.

The product B of the thickness of the substrate 11 and the inverse of the thermal conductivity is
When the value is 1.5 × 10 ⁻² W · m ⁻¹ · K ⁻¹ or more, a deviation of the measured value smaller than 0.001 ° C. can be obtained at the position of the core 13 which is 7.5 μm away from the surface of the substrate 11. A measurement error smaller than this is not required in ordinary temperature measurement of an optical component, and its influence on optical characteristics is negligible.

In practice, if the thermal resistance is high, it becomes difficult to absorb heat for cooling. Therefore, the product B of the thickness of the substrate 11 and the reciprocal of the thermal conductivity is 2.85 × 10 ⁻⁴ W ^−. It is preferable that it is not less than ¹ · m ² · K and not more than 7 × 10 ⁻⁴ W ⁻¹ · m ² · K.

The substrate 11 satisfies the above relationship between the thickness and the thermal conductivity, and functions as a substrate for an optical waveguide, and handles optical signals from an optical integrated circuit substrate, a photoelectric mixed substrate, or the like. Various substrates used as substrates, for example, silicon substrates, plastic electric wiring substrates such as ceramic substrates such as alumina or aluminum nitride, glass ceramic substrates, polyimide substrates, epoxy resin substrates, and PTFE (polytetrafluoroethylene) substrates. Can be used.

Temperature sensor resistor 12 as a temperature detecting element
Is made of a metal or a semiconductor (including their alloys), as long as the resistance changes according to the temperature. Various side temperature resistors and thermistors can be used. Alternatively, it is also possible to use a thermocouple that generates electromotive force by the Seebeck effect by connecting different kinds of metals.

Among them, platinum is suitable as a side temperature resistance material because it is chemically and thermally stable and has high purity. At room temperature, the resistivity is 1.06 × 10 ⁻⁷ Ωm, and the temperature coefficient of resistance is + 0.392% / ° C. The resistance value is desirably 1.0 Ω or more, as the resistance is higher than the resistance of the wiring conductor, because the resistance is less affected by the temperature dependence of the wiring resistance. When the resistance value is too large, the detection value of the current becomes small unless a high voltage is applied to the detection of the resistance value, and the detection sensitivity becomes low. Because self-heating occurs,
It is not suitable as a temperature sensor. Therefore, the resistance value is desirably 10 KΩ or less.

Such a resistor 12 for a temperature sensor is manufactured by a vacuum evaporation method, a sputtering method, a plating method, a screen printing method, or the like, and the film thickness is increased when the height difference from the surface of the substrate 11 is large. Since it is difficult to fabricate an optical waveguide in a planar shape, it is preferable that the
m or less.

The core part 13 and the clad part 14 of the optical waveguide
As the organic optical material for forming the resin, siloxane-based polymer, polyimide, benzocyclobutene, PMMA (polymethyl methacrylate), polycarbonate, norbornene resin, fluororesin, or the like may be used.
Is selected such that the refractive index of the cladding 14 is larger than the refractive index of the cladding 14. In order to form an optical waveguide using these materials, a film is formed on the substrate 11 by a spin coating method, a roll coating method, a spray coating method, or the like, and a photolithography method and RIE (reactive An ion etching) process may be used.

[0030]

Next, specific examples of the photoelectric mixed substrate of the present invention will be described.

A temperature sensor resistor 12 made of a metal conductor film
Was disposed on the upper surface of the substrate 11 below the core portion 13 as a temperature detection element, thereby producing a Mach-Zehnder optical switch as the photoelectric mixed substrate of the present invention.
As shown in FIG. 1 and FIG. 2, this is composed of a substrate 11, a resistor 12 for a temperature sensor, a core 13 of an optical waveguide layer, a clad portion 14 of an optical waveguide layer, and a resistor 15 for temperature control. . Further, cooling was performed by bringing a Peltier element into contact with the lower surface of the substrate 11. As a result, a current is caused to flow through the temperature control resistor 15 to generate heat, heat the core portion 13 of the optical waveguide, and perform switching by changing the optical path length of the optical waveguide.

The dimensions of the substrate 11 are 20 mm in length and 10 mm in width.
And four types having thicknesses of 0.5, 1.0, 1.2, and 1.5 mm were used. Glass ceramic (thermal conductivity: 4 W · m ⁻¹ · K ⁻¹ ) was used as the material of the substrate 11. In the optical waveguide, the cladding portion 14 is made of a siloxane-based polymer (thermal conductivity: 0.5 W · m).
^The core portion 13 of ^-1 · K ^-1 ) was formed by applying a mixed solution of a siloxane-based polymer and tetra-n-butoxytitanium and performing heat treatment at 85 ° C./30 minutes and 270 ° C./60 minutes. SOA
(Semiconductor optical amplifying element) The mounting part and its electrode
It was formed by removing the optical waveguide material by the method.

The core 13 of the optical waveguide is 5 μm × 5 μm, and the thickness of the cladding 14 from the core 13 to the upper surface of the substrate 11 is 5 μm.
m. Therefore, the distance from the center of the core portion 13 to the upper surface of the substrate 11 on which the temperature sensor resistor 12 is formed is 7.5 μm.
Becomes

The temperature control resistor 15 is provided at the core 13 of the optical waveguide.
Formed of Al so as to be located on the upper surface of. When an electric current is applied to this, heat is generated and the optical path length of the core portion 13 of the optical waveguide changes.

The temperature sensor resistor 12 is disposed below the optical waveguide heated by the temperature control resistor 15 on the substrate 11, and the sensor portion located below the core portion 13 of the optical waveguide is Ti. / Pt and Ti / Pt / Au except for the sensor part. The resistance value of the sensor portion was 100Ω, and the other values were 0.2Ω. The thicknesses of Ti and Pt were 0.1 μm and 0.2 μm, respectively.

Then, for these photoelectric mixed substrates,
Light from an LD (laser diode) having a power of 10 dBm and a wavelength of 1.3 μm is made incident on the core portion 13 of the optical waveguide through a single-mode optical fiber, propagates therethrough, and optically connects the single-mode optical fiber to the other end face. The intensity of the emitted light was examined. Then, the temperature of the core 13 is measured by the temperature sensor resistor 12 on each of the opto-electron mixed substrates, and the difference between the temperature at the phase at which the light intensity is the strongest and the temperature at the phase at the weakest is obtained by switching. Was.

In the photoelectron mixed substrate as described above, the product A of the reciprocal of the thermal conductivity of the optical waveguide and the distance from the center of the core 13 to the substrate 11 is 7.5 (μm) /0.5 (W · m ^−1).・ K ^-1 )
= 1.5 × 10 ^-5 (W ^-1 · m ² · K). And the substrate
The difference between the thickness 11 and the thermal conductivity of the substrate 11, the substrate thickness / thermal conductivity, that is, the above-mentioned product B · A / B from the design value of 4 ° C. was examined. The results are shown in Table 1.

[0038]

[Table 1]

From the results shown in Table 1, the product A of the reciprocal of the thermal conductivity of the optical waveguide and the distance from the center of the core 13 to the surface of the substrate 11 is obtained.
However, A / B ≧ 19 with respect to the product B of the reciprocal of the thermal conductivity of the substrate 11 and the thickness of the substrate 11, and the product B is 2.85 × 10 ^−4.
W is ^-1 · m ² · K or more, the substrate thickness is 1.2mm and 1.
In the case of 5 mm, the temperature difference from the design value is smaller than 0.2 ° C., indicating that the temperature of the core 13 can be measured more accurately. Accordingly, since the accuracy of the temperature measurement is within 0.2 ° C., that is, within 5% with respect to 4 ° C., the error of the phase shift is reduced to 0.05π or less, and it is understood that good optical characteristics can be obtained.

As a result, the photoelectric mixed substrate of the present invention
It was confirmed that the substrate was a photoelectric mixed substrate having high temperature detection accuracy for the optical waveguide.

It should be noted that the above is only an example of the embodiment of the present invention, and the present invention is not limited to the embodiment. Various changes and improvements may be made without departing from the gist of the present invention. No problem. For example, the product B of the reciprocal of the thermal conductivity and the thickness of the entire substrate may be adjusted by bonding a plurality of substrates having different thermal conductivity.

[0042]

As described above, according to the optoelectronic mixed substrate of the present invention, the mounting portion of the optical component and the electronic component, the optical waveguide to which the optical component is connected, and a part of the optical waveguide are provided on the substrate. And a temperature detecting element made of metal or semiconductor for detecting the temperature of the optical waveguide, which is arranged in close proximity to the substrate surface from the reciprocal of the thermal conductivity of the optical waveguide and the center of the core of the optical waveguide. To the product B of the inverse of the thermal conductivity of the substrate and the thickness of the substrate, A / B ≧ 19
As a result, the thermal resistance of the optical waveguide becomes relatively smaller than the thermal resistance of the substrate, and the temperature of the upper surface of the substrate becomes closer to the temperature of the center of the core of the optical waveguide than the temperature of the lower surface of the substrate. The temperature difference between the core of the optical waveguide and the surface of the substrate on which the temperature detection element is placed is reduced, and the temperature of the core of the optical waveguide to be measured is accurately measured and detected. It became possible to do.

According to the photoelectric mixed substrate of the present invention,
The product B of the reciprocal of the thermal conductivity of the substrate and the thickness of the substrate is 2.85 × 10
^-4 W ^-1 · m ² · K or more, thermo-optic (TO)
Even for organic optical waveguide materials sensitive to the effects, the above A /
Since B can be set to 19 or more, it has become possible to more accurately measure the temperature of the core portion of the optical waveguide as the device under test.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a photoelectric mixed substrate on which a Mach-Zehnder type all-optical switch is formed as an example of an embodiment of a photoelectric mixed substrate of the present invention.

FIG. 2 is a cross-sectional view taken along line AA ′ of the photoelectric mixed substrate shown in FIG.

FIG. 3 is a cross-sectional view showing an optical delay device using a thermo-optic effect (TO effect) as an example of an optical waveguide substrate provided with a conventional temperature sensor.

FIG. 4 is a cross-sectional view of an optical waveguide used in the optical delay device of FIG.

[Explanation of symbols]

 11 ... substrate 12 ... resistor for temperature sensor (temperature detecting element) 13 ... core part of optical waveguide 14 ... clad part of optical waveguide 15 ... resistor 21 for temperature control substrate

Claims (2)

[Claims] An optical waveguide to which an optical component and an electronic component are mounted on a substrate, an optical waveguide to which the optical component is connected, and a temperature of the optical waveguide disposed close to a lower portion of the optical waveguide. A temperature detecting element made of a metal or a semiconductor is formed, and the product A of the reciprocal of the thermal conductivity of the optical waveguide and the distance from the center of the core portion of the optical waveguide to the surface of the substrate is defined as the thermal conductivity of the substrate. A / E mixed substrate, wherein A / B ≧ 19 with respect to a product B of a reciprocal of the ratio and a thickness of the substrate. 2. The product according to claim 1, wherein the product B of the reciprocal of the thermal conductivity of the substrate and the thickness of the substrate is not less than 2.85 × 10 ⁻⁴ W ⁻¹ · m ² · K. Photo-electron mixed substrate.