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US 2003/0169478 A1Published application
Optical modulator and design method therefor
AssigneeFujitsu Limited
InventorsMasaki Sugiyama, Tadao Nakazawa
Life of this patent
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Abstract
A high-speed, high-performance optical modulator operating with a reduced drive voltage without sacrificing modulation bandwidth. The modulator has an optical waveguide fabricated on a crystal substrate. A signal electrode is on a ridge on the substrate. Ground electrodes are formed on both sides of the signal electrode. A gap between the signal and ground electrodes is at least 44 μm, and an interaction length of the signal electrode is at least 41 mm. The modulator can operate at 40 Gbps or higher.
Claims97
An apparatus comprising:
- an optical modulator comprising
- a ridge;
- a signal electrode on the ridge, the signal electrode having an interaction length which is at least 41 mm;
- and
- a ground electrode, wherein a gap width between the ground electrode and the signal electrode is at least 44 μm.
2 more elements
An optical modulator for optically modulating a light, comprising
- a substrate;
- an optical waveguide through which the light travels;
- a ridge changing an elevation of the optical waveguide with respect to the substrate;
- a ground electrode;
- a signal electrode on the ridge, a gap width between the ground electrode and the signal electrode being at least 44 μm, the signal electrode having an interaction length with respect to the optical waveguide of at least 41 mm, a drive signal supplied to the signal electrode causing an electric field to be produced along the optical waveguide as the light travels through the optical waveguide, to optically modulate the light.
2 more elements
An optical modulator for optically modulating a light, comprising
- a substrate;
- an optical waveguide through which the light travels;
- a ridge changing an elevation of the optical waveguide with respect to the substrate;
- first and second ground electrodes;
- a signal electrode on the ridge and positioned between the first and second ground electrodes, a gap width between the first ground electrode and the signal electrode, and between the second ground electrode and the signal electrode, being at least 44 μm, the signal electrode having an interaction length with respect to the optical waveguide of at least 41 mm, a drive signal supplied to the signal electrode causing an electric field to be produced along the optical waveguide as the light travels through the optical waveguide, to optically modulate the light.
2 more elements
An optical modulator for optically modulating a light, comprising
- a z-cut LiNbO3 substrate;
- an optical waveguide through which the light travels;
- a ridge changing an elevation of the optical waveguide with respect to the substrate;
- first and second ground electrodes;
- a signal electrode on the ridge and positioned between the first and second ground electrodes, a gap width between the first ground electrode and the signal electrode, and between the second ground electrode and the signal electrode, being at least 44 μm, the signal electrode having an interaction length with respect to the optical waveguide of at least 41 mm;
- and
- a buffer layer between the signal electrode and the ridge, wherein a drive signal supplied to the signal electrode causes an electric field to be produced along the optical waveguide as the light travels through the optical waveguide, to optically modulate the light.
4 more elements
An optical modulator comprising
- a crystal substrate that exhibits an electro-optic effect;
- an optical waveguide through which a light travels;
- a ridge changing an elevation of the optical waveguide with respect to the substrate;
- first and second ground electrodes;
- a signal electrode on the ridge and between the first and second ground electrodes, a gap width between the signal electrode and the first ground electrode, and between the signal electrode and the second ground electrode, being at least 44 μm, the signal electrode having an interaction length with respect to the optical waveguide of at least 41 mm, wherein
- the light traveling through the optical waveguide is phase-matched with a microwave signal traveling through the signal electrode, and
- characteristic impedance of the signal electrode is set within a range where microwave reflection is limited below a predetermined level, to thereby optically modulate the light.
4 more elements
An optical modulator comprising
- a z-cut LiNbO3 substrate;
- an optical waveguide through which a light travels;
- a ridge changing an elevation of the optical waveguide with respect to the substrate;
- first and second ground electrodes;
- a signal electrode on the ridge and between the first and second ground electrodes, a gap width between the signal electrode and the first ground electrode, and between the signal electrode and the second ground electrode, being at least 44 μm, the signal electrode having an interaction length with respect to the optical waveguide of at least 41 mm, and
- a buffer layer between the signal electrode and the ridge, wherein
- the light traveling through the optical waveguide is phase-matched with a microwave signal traveling through the signal electrode, and
- characteristic impedance of the signal electrode is set within a range where microwave reflection is limited below a predetermined level, to thereby optically modulate the light.
5 more elements
An apparatus comprising:
- a 40 Gbps optical modulator comprising
- a substrate;
- a signal electrode formed on the substrate, the signal electrode having a base with a width W;
- and
- a ground electrode, a gap width S existing between the ground electrode and the signal electrode, wherein the ratio S/W is greater than or equal to 8.
2 more elements
An apparatus comprising:
- a 40 Gbps optical modulator comprising
- a substrate;
- first and second ground electrodes formed on the substrate;
- and
- a signal electrode formed on the substrate between the first and second ground electrodes, a gap width S existing between the first ground electrode and the signal electrode, and between the second ground electrode and the signal electrode, the signal electrode having a base with a width W, wherein the ratio S/W is greater than or equal to 8.
2 more elements
A method of designing an optical modulator which performs electrical-to-optical conversion by modulating a light beam with a microwave signal, the method comprising the steps of:
- (a) defining an allowable range of characteristic impedance within which microwave reflection is limited below a predetermined level;
- (b) performing phase matching by making effective refraction index for the microwave signal agree with that for the light beam;
- (c) defining a first relationship that associates the thickness of ground electrodes with the width of a gap between a signal electrode and the ground electrodes, based on a result of said phase matching step (b);
- (d) defining a second relationship that associates ground electrode thickness with the gap width within the allowable range;
- (e) determining an acceptable range of the gap width and the ground electrode thickness, based on the first and second relationships;
- (f) plotting the driving voltage and an interaction length of the signal electrode within the acceptable range;
- and
- (g) obtaining optimal values of the gap width, interaction length, drive voltage, and ground electrode thickness by increasing the gap width together with the interaction length to reduce the drive voltage and loss of high-frequency components of the microwave signal.
5 more elements
Dependencies are inferred from the claim text.