US 6,687,039 B2 · Optical modulator

Abstract

To attain a low-voltage driving, a high optical output, a wide band, and better return loss, an optical modulator is provided with an optical waveguide 1 for propagating inputted light, an optical modulator part 2 for varying an intensity of light by applying voltage, a modulator driver circuit 3 for producing or amplifying an electrical signal to be communicated, a terminal resistor 4 disposed on an end opposite to the driver circuit with respect to the optical modulator part, a transmission line 5 which is disposed between the driver circuit and the optical modulator part and transmits an electrical signal to the optical modulator part, and a transmission line 6 disposed between the optical modulator part and the terminal resister. When both ends of a width in parallel with the optical waveguide of the optical modulator are extended perpendicularly to the direction of the optical waveguide to form straight lines 7 and 8, an electrical signal inputted from the driver circuit to the optical modulator part strides over (intersects) the straight line 7 or 8 and at least a part of at least one of the transmission lines 5 and 6 has characteristic impedance larger than output impedance of the driver circuit 3.

Drawings

Claims19

Dependent claims

An optical transmitter, comprising:

an optical waveguide having a substantially straight line on a plane;
and
an optical modulator sandwiched in the optical waveguide on the substantially straight line of the optical waveguide, said optical modulator having an electrical transmission line portion passing through an upper part of the optical modulator and a ground electrode provided on a lower part of the optical modulator, the optical modulator performs a modulating operation by applying voltage between the electrical transmission line portion on the upper part of the optical modulator serving as an electrode and the ground electrode on the lower part of the optical modulator,
wherein first and second straight reference lines provided so as to sandwich the optical modulator on both ends with respect to a light propagation direction of the optical modulator, the first and second straight reference lines extending perpendicularly to the light propagation direction,
a path of an electrical transmission line is provided in series from a modulator driver circuit via said electrical transmission line portion of the optical modulator to a terminal resistor, said terminal resistor is positioned on the opposite side to the modulator driver circuit with respect to the optical modulator, and said path of the electrical transmission line is provided so as to traverse the first and second straight reference lines, and
a section from the driver circuit to the modulator crossed by said first straight reference line serves as a first electrical transmission line, a section from the modulator to the terminal resistor serves as a second electrical transmission line, at least part of a section of at least one of the first and second electrical transmission lines has a larger characteristic impedance than output impedance of the driver circuit, and said characteristic impedance of said first and second electrical transmission lines is larger than that of the electrical transmission line portion of the optical modulator.

3 more elements

An optical modulator, comprising:

an optical waveguide having a substantially straight line on a plane;
and
an optical modulator sandwiched in the optical waveguide on the substantially straight line of the optical waveguide, said optical modulator having an electrical transmission line portion passing through an upper part of the optical modulator and a ground electrode provided on a lower part of the optical modulator, the optical modulator performs a modulating operation by applying voltage between the electrical transmission line portion on the upper part of the optical modulator serving as an electrode the ground electrode on the lower part of the optical modulator,
wherein first and second straight reference lines provided so as to sandwich the optical modulator on both ends with respect to a light propagation direction of the optical modulator, the first and second straight reference lines extending perpendicularly to the light propagation direction,
a path of an electrical transmission line is provided in series from a modulator driver circuit via said electrical transmission line portion of the optical modulator to a terminal resistor, said terminal resistor is positioned on the opposite side to the modulator driver circuit with respect to the optical modulator, and said path of the electrical transmission line is provided so as to traverse the first and second straight reference lines, and
a section from the driver circuit to the modulator crossed by said first straight reference line serves as a first electrical transmission line, a section from the modulator to the terminal resistor serves as a second electrical transmission line, the electrical transmission line portion of the optical modulator is a straight line, the first or second electrical transmission line crosses at an angle of less than 90° with the electrical transmission line portion of the optical modulator, and at least part of a section of at least one of the first and second electrical transmission lines has a larger characteristic impedance than output impedance of the driver circuit, and said characteristic impedance of said first and second electrical transmission lines is larger than that of the electrical transmission line portion of the optical modulator.

3 more elements

An optical modulator, comprising:

an optical waveguide having a substantially straight line on a plane;
and
an optical modulator sandwiched in the optical waveguide on the substantially straight line of the optical waveguide, said optical modulator having an electrical transmission line portion passing through an upper part of the optical modulator and a ground electrode provided on a lower part of the optical modulator, the optical modulator performs a modulating operation by applying voltage between the electrical transmission line portion on the upper part of the optical modulator serving as an electrode and the ground electrode on the lower part of the optical modulator,
wherein first and second straight reference lines provided so as to sandwich the optical modulator on both ends with respect to a light propagation direction of the optical modulator, the first and second straight reference lines extending perpendicularly to the light propagation direction,
a path of an electrical transmission line is provided in series from a modulator driver circuit via said electrical transmission line portion of the optical modulator to a terminal resistor, said terminal resistor is positioned on the opposite side to the modulator driver circuit with respect to the optical modulator, and said path of the electrical transmission line is provided so as to traverse the first and second straight reference lines,
a section from the driver circuit to the modulator crossed by said first straight reference line serves as a first electrical transmission line, a section from the modulator to the terminal resistor serves as a second electrical transmission line, the electrical transmission line portion of the optical modulator is a straight line, and a total length of the electrical transmission line formed into a straight line between the first and second electrical transmission lines is shorter than a wavelength of an electrical signal inputted to the modulator, and
at least part of a section of at least one of the first and second electrical transmission lines has a larger characteristic impedance than output impedance of the driver circuit, and said characteristic impedance of said first and second electrical transmission lines is larger than that of the electrical transmission line portion of the optical modulator.

4 more elements

Dependencies are inferred from the claim text.

Description3,500 words

Summary1,759 words

#The present invention relates to an optical modulator, and particularly to a traveling wave optical modulator and an optical communication light source in optical communication systems.

#A faster light source for optical communication has been demanded for an optical communication system. Currently, a communication system with a transmitting speed of 10 Gbit/s for each channel has been already put into practical use, and a system with a transmitting speed of 40 Gbit/s for each channel has been developed for practical use. As an optical communication light source used in such a high-speed optical communication system, an optical modulator has been adopted.

#As an optical modulator, two kinds of an electroabsorption modulator and a Mach-Zehnder type modulator have been used. For example, as technique for achieving a wide-band modulator as an electroabsorption modulator, JP-A-2000-258739 discloses that a modulator is divided to reduce a capacitance thereof, thereby achieving a wide-band modulator with a high extinction ratio.

Brief description of the drawings11 figures

#FIG. 1 shows a basic configuration and a driver circuit of an optical modulator according to Embodiment 1 of the present invention;

#FIG. 2 is a cross-sectional view taken along line 14 on a modulator part of the basic configuration of the optical modulator according to Embodiment 1;

#FIG. 3 is a cross-sectional view taken along line 15 on a high impedance line of the basic configuration of the optical modulator according to Embodiment 1;

Detailed description1,519 words

#[Embodiment 1]

#FIG. 1 shows an upper part of an element of Embodiment 1 according to the present invention, which adopts an electroabsorption modulator using MQW as an optical modulator part. The modulator is composed of an electroabsorption optical modulator part 2 and an optical waveguide 1, which is disposed on the right and left of the electroabsorption optical modulator part 2. The optical modulator part absorbs light by applying an electric field between a ground 13 and an electrode connecting transmission lines 5 and 6. Hence, an electrical signal is converted to an optical signal.

#FIG. 2 is a cross-sectional view taken along line 14 on the optical modulator part. Reference numeral 21 in FIG. 2 denotes an electrode constituting a transmission line. The following layer structure is provided right below the electrode.

Facts

Application

09/941,651Filed 30 Aug 2001

Priority

JP 2001-2029124 Jul 2001

Published

US 2003/0007228 A19 Jan 2003

Granted

3 Feb 2004

Term ended

31 Oct 2021

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment, including 62 days of adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification5 codes

G02F 1/0356
In an optical waveguide structure: controlled by a high-frequency electromagnetic wave component in an electric waveguide structure
B82Y 20/00
Nanooptics
G02F 1/01708
Structures with periodic or quasi periodic potential variation, e.g. superlattices, quantum wells: in an optical wavequide structure
G02F
Optical devices or arrangements for the control of light by modification of

Timeline

4 Jul 2001Priority claimedJP 2001-202912
30 Aug 2001Application filedUS 09/941,651
21 Nov 2001Assigned to Hitachi, Ltd.assignment of assignor's interest
9 Jan 2003PublishedUS 2003/0007228 A1
3 Feb 2004GrantedUS 6,687,039 B2
30 Aug 2012Assigned to Opnext Japan, Inc.assignment of assignor's interest
3 Dec 2014Assigned to Oclaro Japan, Inc.change of name
31 Oct 2021Term endedEstimated, includes 62 days of adjustment

Optical modulator

Life of this patent

Optical modulator

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims19

Description3,500 words

Drawings

Classification5 codes

Life of this patent

Description3,500 words