Optical SSB modulator

• US 20050220385A1
• Filed: 03/22/2005
• Published: 10/06/2005
• Est. Priority Date: 03/24/2004
• Status: Active Grant

• Current Assignee: National Institute of Information and Communications Technology, Sumitomo Osaka Cement Company Limited
• Original Assignee: National Institute of Information and Communications Technology, Sumitomo Osaka Cement Company Limited
• Inventors: Kawanishi, Tetsuya, Mori, Shingo, Higuma, Kaoru, Izutsu, Masayuki
• Granted Patent: US 7,239,763 B2
• Time in Patent Office: Days
• US Class Current: 385/1
• CPC Class Codes: G02F 1/0123 Circuits for the control or stabilisation of the bias voltage, e.g. automatic bias control [ABC] feedback loops
• CPC Class Codes: G02F 1/035 in an optical waveguide structure
• CPC Class Codes: G02F 1/212 Mach-Zehnder type
• CPC Class Codes: G02F 1/225 in an optical waveguide structure
• CPC Class Codes: G02F 1/3136 of interferometric switch type

Abstract

An optical SSB modulator capable of appropriately adjusting a phase difference of light in the MZ waveguides and automatically adjusting a voltage impressed to the bias adjustment electrodes is provided. The above-mentioned object is achieved by an optical SSB modulator (1) provided with a first sub Mach-Zehnder waveguide (MZ_A) (2), a second sub Mach-Zehnder waveguide (MZ_B) (3), a main Mach-Zehnder waveguide (MZ_C) (4), a first bias adjustment electrode (DC_A electrode) (5), a second bias adjustment electrode (DC_B electrode) (6), a first modulation electrode (RF_A electrode) (7), a second modulation electrode (RF_B electrode) (8) and a third bias adjustment electrode (DC_C electrode) (9), wherein either one of or both of output portions (10, 11) of the MZ_A and the MZ_B have an X-branching form, and specifically having one of light paths of the X-branching connected to a photodetector.

Claims

1. An optical single side band (SSB) modulator comprising one or more sub Mach-Zehnder waveguides, wherein:

an output portion of at least one sub Mach-Zehnder waveguide among the sub Mach-Zehnder waveguides has an X-branching form; and

among two waveguides stretching from the X-branching formed output portion, one waveguide is connected to a photodetector for measuring a light intensity, and a remaining waveguide is a waveguide for an output light from the optical modulator.

4. The optical SSB modulator as claimed in any one of claims 1-3, wherein the X-branching is an asymmetrical X-branching.

5. The optical SSB modulator as claimed in claim 4, wherein one light path of the X-branching is connected to a photodetector.

6. The optical SSB modulator as claimed in any one of claims 1-3, further comprising:

a photodetector connected to one light path of the X-branching;

a control apparatus receiving information related to an amount of unnecessary light from the photodetector, obtaining voltage adjustment information for adjusting an amount of voltage impressed to a bias adjustment electrode of a sub Mach-Zehnder waveguide based on the information, and outputting the voltage adjustment information; and

a first signal source impressing a voltage to the bias adjustment electrode of the sub Mach-Zehnder waveguide based on the voltage adjustment information outputted from the control apparatus.

9. An optical frequency shift keying modulator comprising the optical SSB modulator as claimed in claim 4, wherein a combination of a modulation electrode and a bias adjustment electrode or a modulation electrode is substituted for the third bias adjustment electrode.

10. An optical frequency shift keying modulator comprising the optical SSB modulator as claimed in claim 5, wherein a combination of a modulation electrode and a bias adjustment electrode or a modulation electrode is substituted for the third bias adjustment electrode.

2. An optical SSB modulator comprising:

a first sub Mach-Zehnder waveguide;

a second sub Mach-Zehnder waveguide;

a main Mach-Zehnder waveguide provided with the first sub Mach-Zehnder waveguide and the second sub Mach-Zehnder waveguide;

a first bias adjustment electrode controlling a bias voltage between two arms composing the first sub Mach-Zehnder waveguide, thereby controlling a phase of light propagating in the two arms of the first sub Mach-Zehnder waveguide;

a second bias adjustment electrode controlling a bias voltage between two arms composing the second sub Mach-Zehnder waveguide, thereby controlling a phase of light propagating in the two arms of the second sub Mach-Zehnder waveguide;

a first modulation electrode inputting a radio frequency signal to the two arms composing the first sub Mach-Zehnder waveguide;

a second modulation electrode inputting a radio frequency signal to the two arms composing the second sub Mach-Zehnder waveguide; and

a third bias adjustment electrode controlling the bias voltages of the first and second sub Mach-Zehnder waveguides, thereby controlling a phase of light propagating in the first and second Mach-Zehnder waveguides,

wherein an output portion of either one of or both of the first and second sub Mach-Zehnder waveguides has an X-branching form.

7. An optical frequency shift keying modulator comprising the optical SSB modulator as claimed in claim 2, wherein a combination of a modulation electrode and a bias adjustment electrode or a modulation electrode is substituted for the third bias adjustment electrode.

3. An optical SSB modulator comprising:

a first sub Mach-Zehnder waveguide;

a second sub Mach-Zehnder waveguide;

a main Mach-Zehnder waveguide provided with the first sub Mach-Zehnder waveguide and the second sub Mach-Zehnder waveguide;

a first modulation electrode inputting a radio frequency signal and a signal related to a bias voltage to two arms composing the first sub Mach-Zehnder waveguide;

a second modulation electrode inputting a radio frequency signal and a signal related to a bias voltage to two arms composing the second sub Mach-Zehnder waveguide; and

a third bias adjustment electrode controlling the bias voltages of the first and second sub Mach-Zehnder waveguides, thereby controlling a phase of light propagating in the first and second Mach-Zehnder waveguides,

wherein an output portion of either one of or both of the first and second sub Mach-Zehnder waveguides has an X-branching form.

8. An optical frequency shift keying modulator comprising the optical SSB modulator as claimed in claim 3, wherein a combination of a modulation electrode and a bias adjustment electrode or a modulation electrode is substituted for the third bias adjustment electrode.