LiNbO3 Optical Single-Sideband Modulator

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LiNbO3 Optical Single-Sideband Modulator
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2
Outline

• Introduction
• Principle of Operation
• Experiment and Results
• Summary
• References

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Introduction

• Single-Sideband (SSB) Modulator
• Material
• z-cut lithium niobate (LN)
• Fabrication
• titanium diffusion
• Advantages
• Increase bandwidth efficiency
• Reduce dispersion penalty
• Suppress nonlinear effect

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Principle of Operation

• The integrated modulator consists of parallel
  Mach-Zehnder (MZ) intensity modulator with four
  optical modulation waveguides.

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Signal Diagram

• Each frequency diagram shows Bessel function
  profiles
• of J-4 to J4.

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Optical Output Signals

• In-phase modes are
• Out-of-phase modes are

• wc optical carrier angular frequency
• wm modulation angular frequency
• mf modulation index

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Experiment

• Block diagrams of the SSB modulation measurement.

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Measured Optical Spectra

• Measured optical spectra of the SSB modulation.
  The dotted line shows the spectrum of a DFB-LD.

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Optical Power vs Driving Voltage

• Relationship between optical power of J-1 and
  J3modes and driving voltage.

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Modulated Optical Spectra
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Reduce Dispersion Penalty

• Double sideband spectrum is susceptible to
  chromatic dispersion. Using SSB modulation will
  reduce dispersion penalty.

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Suppress Nonlinear Effect

• Without centered-cubic lattice(like LN), the
• polarization vector is

• Reduce driving power to suppress the nonlinear
  effects in LN modulators.

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Disadvantages

• Using three Y-branches makes the on/off
  extinction ratio degraded.

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Improved Structure

• Using a Y-branch to improve the on/off extinction
  ratio.

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Summary

• Optical SSB modulation with suppressions J0 and
  J3 of a 10GHz signal in a driving voltage of
  6.3Vp-p
• Advantages
• Increase bandwidth efficiency
• Reduce dispersion penalty
• Suppress nonlinear effect
• Disadvantage
• Degrade on/off extinction ratio

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References

1. S. Shimotsu, S. Oikawa, T. Saitou, N. Mitsugi,
   K. Kubodera, T. Kawanishi, and M. Isutsu, Single
   Side-Band Modulation Performance of a LiNbO3
   Integrated Modulator Consisting of Four-Phase
   Modulator Waveguides,IEEE Photon. Technol.
   Lett., Vol. 13., No. 4, April 2001.
2. R. Hui, Senior Member, IEEE, B. Zhu, R. Huang, C.
   Allen, Senior Member, IEEE, K. Demarest, and D.
   Richards, 10Gb/s SCM Fiber System Using Optical
   SSB Modulation, IEEE Photon. Technol. Lett. Vol.
   13., No. 8, August 2001.
3. A. Loayssa, D. Benito, and M. J. Garde
   Single-Sideband Suppressed-Carrier Modulation
   Using a Single-Electrode Electrooptic Modilator,
   IEEE Photon. Technol. Lett., Vol. 13., No. 8,
   August 2001.