Heater module and optical waveguide module

Details Heater module and optical waveguide module Heater module and optical waveguide module

2001-09-24

2003-09-09

Cherry, Euncha (Department: 2872)

Optical waveguides

Accessories

External retainer/clamp

C385S092000

Reexamination Certificate

active

06618539

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heater module for heating an optical waveguide device so as to regulate the temperature of the optical waveguide device, and an optical waveguide device equipped with the same.
2. Related Background Art
If an optical waveguide module has a large temperature distribution within an optical waveguide device, the size of the optical waveguide will vary due to differences in thermal expansion of its substrate depending on locations, thereby damaging its wavelength selectivity and switching characteristics. Therefore, an uniformity in temperature is required within the optical waveguide device.
As a device for regulating the temperature of optical waveguide devices, thermoelectric cooling module and heaters have conventionally been utilized. Since it is necessary for an optical waveguide module to draw thereinto an optical fiber used for transmitting optical signals with respect to external devices, hermetic sealing is difficult at the drawing portion. Therefore, it is impossible for thermoelectric cooling module to secure their reliability, whereby heaters are often used as a temperature-regulating device. In a heater, a heat-generating circuit (resistance) adapted to generate heat when energized is provided within an insulating layer, whereby the heat from the heat-generating circuit is transmitted to the optical waveguide device by way of the insulating layer.
Conventionally, ceramics heaters made of alumina having a relatively low thermal conductivity (thermal conductivity of 20 W/mK) and the like have often been used. However, tendencies toward larger capacities and higher-speed communications have nowadays become remarkable, in particular, in the field of optical communications. Recently, along with the shift to D-WDM (Dense Wavelength Division Multiplexing), optical waveguide devices having large areas have come into use. Further, there has been an increasing demand for multiplexing a greater number of signals than those conventionally multiplexed for a certain frequency width, thereby enhancing the demand for uniformity in temperature. Hence, it is desired that the uniformity in temperature within the optical waveguide device be further improved (to become ±0.5° C. or less).
In order to satisfy such a demand for uniformity in temperature of the optical waveguide device, two methods have currently been under consideration. The first method is one using a heat spreader employing a Cu alloy or the like having a favorable thermal conductivity. It is a method in which the heat generated by an alumina heater is once uniformly dispersed by the heat spreader and then is transmitted to the optical waveguide device, so as to improve the uniformity in temperature. The second method is one in which the heater itself is formed from AlN or the like having a thermal conductivity (thermal conductivity of 170 W/mK) which is about 10 times that of conventionally used alumina, so that the heat generated by the heater is uniformly dispersed by the heater itself and then is transmitted to the optical waveguide device, whereby the uniformity in temperature is improved. When these methods are employed, the temperature distribution of the optical waveguide device can be made ±0.5° C. or less.
SUMMARY OF THE INVENTION
However, demands for D-WDM have recently been becoming severer in a drastic manner, whereby further multiplexing is desired. As a consequence, a temperature uniformity higher than that conventionally achieved is required for optical waveguide devices. Further, photonic networks making full use of optical switching and the like without using electric devices at all have been under consideration. For realizing them, devices using new materials such as LiNbO
3
and resin waveguides, which are different from conventional quartz and silica, have been under consideration as optical waveguide devices. For these devices, a temperature uniformity severer than that conventionally demanded is required, and there is a case where a temperature uniformity of ±0.1° C. or less is required for an optical waveguide device.
In order to overcome such problems, as shown in
FIG. 7
, an attempt to realize a temperature uniformity of ±0.1° C. or less was carried out by utilizing the fact that the temperature uniformity of an optical waveguide device
71
improves when the thickness of a ceramics heater
73
or the thickness of a heat spreader
72
is enhanced. In this case, though the temperature uniformity in the optical waveguide device
71
was maintained in its surface bonded to the ceramics heater
73
or heat spreader
72
, the surface opposite from the one bonded to the ceramics heater
73
or heat spreader
72
was exposed to an ambient temperature, whereby the optical waveguide device
71
was cooled, thus failing to realize a temperature uniformity of ±0.1° C. or less.
In order to prevent the upper part of the optical waveguide device
71
from being cooled, there maybe considered a method in which the optical waveguide device
71
is heated by a heater from both upper and lower faces of the optical waveguide device
71
, or a method in which the heater for heating is not constituted by ceramics but by a silicone
74
or polyimide heater, which can be bent freely as shown in
FIG. 8
, and the heater is processed into a tubular form having a center part at which the optical waveguide device
71
is installed.
However, the above-mentioned methods heat not only the optical waveguide device
71
but also the whole optical module, thereby being problematic in that the power consumption increases to about two times or more that in the case where heating is effected from only the lower face of the optical waveguide device
71
. Also, they are problematic in that the optical waveguide module inevitably increases its thickness. While an optical waveguide module is required to have a thickness of about 10 mm, which is typical as a module other than the optical waveguide module, the thickness of the optical waveguide module becomes about 20 to 30 mm in the above-mentioned methods. Therefore, in an apparatus equipped with the optical waveguide module, design rules for designing an apparatus constituted by other devices alone are not applicable, so that a special design is necessary, whereby not only the efficiency in designing and the cost of design, but also the cost of the whole apparatus increases.
Therefore, it is an object of the present invention to provide a heater module which can improve the temperature uniformity in an optical waveguide while keeping the power consumption and the thickness of the optical waveguide module by overcoming the problems mentioned above, and an optical waveguide module equipped therewith.
The heater module in accordance with the present invention is a heater module for heating an optical waveguide device so as to regulate a temperature of the optical waveguide device, the heater module comprising a heat-generating circuit adapted to generate heat when energized; and a heat-transmitting section disposed on an upper face of the heat-generating circuit and formed with a recessed groove portion for mounting the optical waveguide device.
In the present invention, the heat-transmitting section for heating an optical waveguide device is formed with a recessed groove portion, and the optical waveguide device is mounted in this recessed groove portion. The inventors have found that such a configuration makes it possible to heat the optical waveguide device not only from its bottom face but also from its side faces by way of edge parts constituting the recessed groove portion, whereby the temperature uniformity can be enhanced. Since the heat is transmitted from the edge parts of the recessed groove portion formed in the integral heat-transmitting section in the configuration of the present invention, it is not necessary to provide respective heaters
75
for generating heat at the bottom and side faces as shown in FIG.
9
. Also, since the optical waveguide de

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