JPH1144867A - Optical modulator module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the loss of signal light occurring in the shape of a carrier to be mounted with a photodiode for monitor by notching this carrier so as not to shield the optical path of the main signal light radiated from the end face of an optical waveguide. SOLUTION: A modulator chip 20 is mounted on the base of a package 6. An opening 52 for taking out the output light from this modulator chip 20 and a recessed part 54 to be mounted with the chip carrier 46 are formed on the package 6. A notch 46a is formed at the chip carrier 46 in such a manner that part of the chip carrier 46 has an approximately trapezoidal shape in section. Since this notch 46a is formed, the chip carrier 46 does not shield the main signal outputted from the modulator chip 20 any more. Since the shape and size of the chip carrier 46 are previously selected with respect to the shape and size of the package 6, the chip carrier 46 may be positioned at the base and two flanks of the package 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an optical modulator module for modulating light from a light source, and more particularly, to a structure of an optical modulator module for monitoring optical power.

[0002] In recent optical fiber communication systems, the modulation speed is increasing as the transmission speed is increased. In direct intensity modulation of a laser diode, wavelength distortion causes waveform distortion. In order to avoid this problem, there is increasing expectation for optical modulator modules used as external modulators.

[0003]

2. Description of the Related Art As a practical external modulator, a Mach-Zehnder type optical modulator (LN modulator) using a dielectric crystal substrate such as lithium niobate (LiNbO ₃ ) has been developed. A carrier light having a constant intensity from a light source is supplied to the LN modulator, and an optical signal whose intensity is modulated by a switching operation using light interference is obtained.

The LN modulator chip is composed of a pair of optical waveguides coupled near both ends by thermally diffusing titanium to increase the refractive index on the surface of a dielectric substrate made of a Z-cut lithium niobate crystal. Form a wave path,
A buffer layer made of SiO ₂ is formed thereon, and a signal electrode (travelling wave electrode) and a ground electrode are formed on the buffer layer corresponding to the optical waveguide.

[0005] The signal light incident from one end of the optical waveguide is branched and propagates through a pair of optical waveguides. When a drive voltage is applied to a signal electrode formed on one of the optical waveguides, a phase difference occurs between the two signal lights branched by the electro-optic effect.

In the LN modulator, these signal lights are recombined and extracted as an optical signal output. If a drive voltage is applied so that the phase difference between the signal lights propagating through the pair of optical waveguides becomes, for example, 0 or π, an on / off pulse signal can be obtained.

The disadvantages of LN modulators that are often pointed out are:
An operating point shift due to a temperature drift and a DC drift occurs. In order to cope with this operating point shift, the power of light output from the LN modulator is monitored, and control for stabilizing the operating point is performed based on the resulting electric signal.

[0008]

In order to monitor the power of the light output from the optical modulator, a part of the light should be split by an optical coupler and the split light can be received by a photodetector. However, in this case, there is a problem that the power of the optical signal output from the optical modulator is reduced, and the number of components is increased to increase the size of the device.

In view of the above, radiation light (leakage light) radiated from the coupling portion of the waveguide is monitored at the end face of the waveguide using a photodetector, and a change in an electric signal output from the photodetector is monitored. For example, Japanese Patent Application Laid-Open No. 3-145623 proposes a technique for controlling the operating point of an optical modulator by changing the DC bias of an input electric signal applied to a traveling wave electrode (signal electrode).

However, in the prior art, the loss of signal light due to a part of the main signal light being blocked by the chip carrier on which the photodiode provided on the end face of the waveguide is blocked, and the alignment of the chip carrier on which the photodiode is mounted. A lot of man-hours had occurred.

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and it is an object of the present invention to reduce the number of man-hours for alignment of a monitor chip carrier without causing a loss in main signal light. It is an object of the present invention to provide an optical modulator module capable of performing the following.

[0012]

According to the present invention, there is provided a package, and a Mach-Zehnder optical waveguide including a Y-branch portion and a Y-coupling portion formed on a substrate having an electro-optic effect, which is mounted in the package. A modulator chip having a traveling wave electrode and a ground electrode formed on the optical waveguide,
A light detector module having a light detector mounted in the package so as to receive the radiation light generated at the Y-coupling portion of the modulator chip. An optical modulator module is provided, wherein the carrier is cut off so as not to block the optical path of the main signal light emitted from the end face of the optical waveguide while being positioned on the bottom surface and the two side surfaces.

By positioning the carrier on which the photodetector is mounted on the bottom surface and two side surfaces of the package, the number of steps for alignment of the carrier can be reduced. Also,
By providing the cutout in the carrier, loss of the main signal light due to the carrier blocking a part of the main signal light can be prevented.

According to another aspect of the present invention, a Mach-Zehnder optical waveguide including a package, a Y-branch portion and a Y-coupling portion formed on a substrate having an electro-optical effect and mounted in the package; A modulator chip having a traveling wave electrode and a ground electrode formed on a wave path, and a photodetector mounted in the package so as to receive radiated light generated at the Y-coupling portion of the modulator chip. In the optical modulator module, the thickness of the carrier on which the photodetector is mounted is reduced to １ ／ or less of the height of the modulator chip, and the carrier has the same height as the modulator chip. Wherein the photodetector is mounted on a side surface of the carrier.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the appearance of an optical modulator module to which the present invention is applied. The optical modulator module modulates light received at the input port 2 and outputs the modulated light from the output port 4. In this embodiment, ports 2 and 4 are each optical connectors.

This optical modulator module has a package 6 in which a modulator chip described later is built. At both ends of the package 6, there are provided pigtail fiber assemblies 8 and 10 for connecting the ports 2 and 4 to the package 6, respectively. Reference numerals 3 and 5 indicate optical fibers.

On one side of the package 6, high-speed signal connectors 12 and 14 are provided, and on the other side, a low-speed signal connector 16 is provided. A metal fitting 18 is fixed to the bottom of the package 6 to fix the package 6 to a case (not shown).

Referring to FIG. 2, a plan view of the modulator chip 20 incorporated in the package 6 is shown. The modulator chip 20 has a Mach-Zehnder optical waveguide 24 provided by a dielectric chip 22.

The dielectric chip 22 is made of, for example, lithium niobate (LiNbO ₃ ), and forms an optical waveguide 24 by thermal diffusion of titanium (Ti). Optical waveguide 2
4 has a Y branch portion 26 and a Y coupling portion 28. The optical waveguide 24 is branched into a pair of optical waveguides between the Y branch part 26 and the Y coupling part 28.

The signal light supplied to the input terminal 36 is substantially split into two optical powers by the Y branch portion 26 and guided by the respective optical waveguides. This guided light is coupled by the Y coupling section 28 and exits from the exit end 38.

A coupling mode in which an output beam is obtained at an output end 38 in accordance with the phase difference between the light guided through the pair of branch optical waveguides, and a radiation in which light is radiated from the Y coupling portion 28 into the dielectric chip 22. Mode (leakage mode).

To change the phase between the branched signal lights, a signal electrode 30 is provided on one of the optical waveguides, and a ground electrode 32 is provided on the other optical waveguide and on the dielectric chip 22. , 34 are provided.

The signal electrode 30 is of a traveling-wave type, and its input end is connected to the internal conductor of the connector 12.
The output end is connected to the internal conductor of the connector 14. The shields of the connectors 12 and 14 and the ground electrode 3
2 and 34 are grounded via the package 6.

The electrodes 30, 32 and 34 are made of, for example, gold (A
u) is formed by vapor deposition. Although not shown, an SiO ₂ buffer layer for stabilizing the temperature is provided between the dielectric chip 22 and the electrodes 30, 32, and.

Downstream of the Y-coupling portion 28, Ti-doped regions 40 and 42 are provided. Ti-doped region 40,
Reference numeral 42 is provided to guide the radiation emitted from the Y-coupling portion 28 below the dielectric chip 22 as shown in FIG.

Referring to FIG. 3, the signal light from the optical fiber 3 is applied to the input end 36 of the optical waveguide 24 by the aspherical lens 7.
Is combined with On the other hand, the signal light beam 48 from the output end 38 of the optical waveguide 24 is
Is combined with

The radiation emitted from the Y-coupling portion 28 is Ti
It is guided below the dielectric chip 22 by the doped region 40 and is emitted as a radiation light beam 50 from the end face of the chip. The emitted light beam 50 is received by a monitor photodiode (PD) 44 mounted on a chip carrier 46.

The DC bias of the electric signal applied to the signal electrode (travelling wave electrode) 30 is changed by a signal control circuit (not shown) in accordance with the change of the electric signal output from the photodiode 44, and the operation of the modulator chip 20 is performed. Control points.

Referring to FIG. 4, there is shown a positional relationship of the light receiving region 45 of the monitoring photodiode 44 with respect to the emitted light distribution. In FIG. 4, reference numeral 24 denotes an optical waveguide,
0 indicates the emission light distribution, respectively. Reference numeral 46 denotes a chip carrier, and reference numeral 45 denotes a light receiving region of the monitor photodiode 44.

As can be seen from this figure, the monitor area 45 of the emitted light can be disposed relatively below the modulator chip 20, and a sufficient light receiving sensitivity can be obtained at this position.

Next, a first embodiment of the optical modulator module of the present invention will be described with reference to FIGS.
The modulator chip 2 shown in FIG.
0 is mounted. Package 6 includes modulator chip 2
An opening 52 for taking out the output light from 0 and a concave portion 54 for mounting the chip carrier 46 are formed.

The reason why the concave portion 54 is formed on the bottom surface of the package 6 is that the chip carrier 46 needs a certain size from the viewpoint of handleability.
Photodiode chip (PD chip) mounted on 6
This is to make the height of 44 coincide with the receivable position of the radiated light output from the modulator chip 20.

The chip carrier 46 is made of ceramic, and has a gold pattern 56 deposited on its surface as shown in FIG. The PD chip 44 and the gold pattern 56 are bonded and connected by a gold wire 58,
The terminal 60 and the gold pattern 56 are connected by bonding with a gold wire 62. Terminal 60 is connected to connector 16.

In this embodiment, the chip carrier 46 is formed so that a part of the chip carrier 46 has a substantially trapezoidal cross section.
Is formed with a notch 46a. This notch 46
Since a is formed, the main signal light output from the modulator chip 20 is not blocked by the chip carrier 46, and loss of the main signal light due to the chip carrier is prevented. The notch 46a may have any shape as long as it does not block the main signal light.

Since the shape and size of the chip carrier 46 with respect to the shape and size of the package 6 are selected in advance, the chip carrier 46 can be positioned on the bottom surface and the two side surfaces of the package 6. The number of alignment steps can be greatly reduced.

Referring to FIG. 7, there is shown a plan view of a second preferred embodiment of the present invention. FIG. 8 is a sectional view taken along line 8-8 of FIG. In this embodiment, the chip carrier 46A is formed thin, and the mounting surface of the modulator chip 20 and the chip carrier 46A are formed.
The chip carrier 46A does not block the main signal light output from the modulator chip 20 even when the mounting surfaces are set at the same height.

For example, the height of the modulator chip 20 is about 1 m
m, the thickness of the chip carrier 46A is about 500 μm.
m or less. When the chip carrier 46A is made thinner in this way, the handleability is impaired to some extent, but since the concave portion 54 does not need to be formed in the package 6 as in the first embodiment, the structure of the package 6 is simplified.

Also in this embodiment, the chip carrier 4
In addition to the fact that 6A does not block the main signal light output from the modulator chip 20, the chip carrier 46A is positioned on the bottom surface and two side surfaces of the package 6, so that the alignment man-hour of the chip carrier 46A is greatly reduced. can do.

Referring to FIG. 9, there is shown a plan view of a third preferred embodiment of the present invention. FIG. 10 is a sectional view taken along line 10-10 of FIG. In the present embodiment, the side wall 6a of the package 6 defining the opening 52 is formed thick, and the chip carrier 46B is formed.
Has a width of about 500 μm or less.

As described above, even when the side wall 6a of the package is formed thick and the width of the chip carrier 46B is reduced, the same effects as those of the first and second embodiments can be obtained.

[0041]

According to the present invention, loss of signal light due to the shape of a carrier on which a monitor photodiode is mounted can be prevented, and the number of alignment steps when mounting the carrier on a package can be reduced. Can be.

[Brief description of the drawings]

FIG. 1 is a plan view showing an appearance of an optical modulator module.

FIG. 2 is a plan view of a modulator chip.

FIG. 3 is a diagram illustrating a schematic configuration of an optical modulator module.

FIG. 4 is a diagram showing a positional relationship of a monitoring PD with respect to a radiation light distribution.

FIG. 5 is a plan view of the first embodiment of the present invention.

FIG. 6 is a sectional view taken along line 6-6 in FIG. 5;

FIG. 7 is a plan view of a second embodiment of the present invention.

FIG. 8 is a sectional view taken along line 8-8 in FIG. 7;

FIG. 9 is a plan view of a third embodiment of the present invention.

FIG. 10 is a sectional view taken along line 10-10 of FIG. 9;

[Explanation of symbols]

 6 Package 20 Modulator chip 24 Optical waveguide 26 Optical branching part 28 Optical coupling part 30 Signal electrode 32, 34 Ground electrode 40, 42 Ti-doped region 44 Monitoring PD chip 46 Chip carrier 46a Notch

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshihiro Otani 2-1-1 Kitaichijo Nishi, Chuo-ku, Sapporo City, Hokkaido Inside Fujitsu Hokkaido Digital Technology Co., Ltd. (72) Tomoyuki Ito Kitaichijo-Nishi, Chuo-ku, Sapporo, Hokkaido 2-chome 1 Fujitsu Hokkaido Digital Technology Co., Ltd.

Claims (4)

[Claims] A Mach-Zehnder optical waveguide including a package, a Y-branch portion and a Y-coupling portion formed on a substrate having an electro-optic effect, mounted on the package, and formed on the optical waveguide. An optical modulator module comprising: a modulator chip having a traveling-wave electrode and a ground electrode; and a photodetector mounted in the package so as to receive radiation emitted at the Y-coupling portion of the modulator chip. Wherein the carrier on which the photodetector is mounted is positioned on the bottom surface and two side surfaces of the package, and the carrier is cut out so as not to block the optical path of the main signal light emitted from the end face of the optical waveguide. An optical modulator module. 2. The optical modulator module according to claim 1, wherein the bottom surface of the package has a concave portion having a predetermined depth, and the carrier is mounted on the concave portion. A Mach-Zehnder optical waveguide including a Y-branch portion and a Y-coupling portion formed on a substrate having an electro-optical effect, the package being mounted on the package, and formed on the optical waveguide. An optical modulator module comprising: a modulator chip having a traveling-wave electrode and a ground electrode; and a photodetector mounted in the package so as to receive radiation emitted at the Y-coupling portion of the modulator chip. The thickness of a carrier on which the photodetector is mounted is reduced to less than half the height of the modulator chip, and the carrier is mounted on the bottom surface of a package having the same height as the modulator chip. An optical modulator module, wherein the photodetector is mounted on a side surface of the carrier. 4. The optical modulator module according to claim 1, wherein said carrier is made of ceramic.