Optical SSB modulator

• US 7,239,763 B2
• Filed: 03/22/2005
• Issued: 07/03/2007
• 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
• Primary Examiner(s): Bovernick; Rodney
• Assistant Examiner(s): STAHL, MICHAEL J
• Application Number:
  US11/085,609
• Publication Number:
  US 20050220385A1
• Time in Patent Office: 833 Days
• Field of Search: None
• 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; and

a main Mach-Zehnder waveguide provided with the 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.

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.

11. The optical SSB modulator according to claim 1, wherein the X-branching is an asymmetrical X-branching.

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.

4. The optical SSB modulator as in any one of claims 2 and 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.

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.

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.

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.