Electrooptic Tunable Filters for WDM Networks
An attractive component for wavelength division multiplexing (WDM) in fiber optic networks is a four-port, tunable channel-dropping filter . Such components are important to increase the bit rate for high capacity optical networks by better utilization of the fiber bandwidth, and also in switching functions for efficient signal routing. Polarization independence is a key requirement, and high speed (<1 μs) tuning is needed for packet-switching. Tunable wavelength filters have been produced in a number of materials using acoustooptic and electrooptic tuning schemes as well as movable gratings , . This paper discusses the development of electrooptically tunable filters in ferroelectric LiTaO3 crystals. These filters make use of the static strain-optic (SSO) effect for phase matched polarization coupling in diffused channel waveguides. The use of the SSO effect in producing low-loss channel waveguides in LiNbO3 and LiTaO3 substrates, as well as in tungsten bronze Sr0.6Ba0.4Nb2O6 (SBN:60) and BSTN crystals  is also presented. The tungsten bronzes are attractive materials for making channel-dropping filters due to their larger r33 electrooptic coefficients , which could make it possible to increase the number of accessible wavelength channels and reduce electrooptic tuning voltages.
KeywordsLithium Titanate Tungsten Barium Strontium
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- P.E. Green, Jr., Fiber Optic Networks, Englewood Cliffs, NJ: Prentice Hall, 1993.Google Scholar
- Tungsten bronze crystals supplied by Dr. R.R. Neurgaonkar, Rockwell International Science Center.Google Scholar
- R.W. Schmidt and I.P. Kaminow, “Metal diffused optical waveguide in LiNbO3,” AppL Phys. Leet., vol. 25, 1974.Google Scholar
- D.A. Pinnow, “Elastooptical materials,” in Handbook of Lasers, edited by R.J. Presley, Cleveland, OH: CRC, 1971.Google Scholar
- J.M. Marx, O. Eknoyan, H.F. Taylor, and R.R. Neurgaonkar, “Low loss optical waveguides in strontium barium niobate (SBN:60) at 1.3.tm wavelength,” submitted for publication.Google Scholar
- K. Yamanouchi, K. Wakazono, and K. Shibayama, “Optical surface wave mode converters and modulators utilizing static strain optic effects,” IEEE J. Quantum Electron., vol. QE-16, pp. 628–634, 1980.Google Scholar
- Z. Tang, O. Eknoyan, and H.F. Taylor “Polarization-independent electrooptically tunable wavelength filter in LiTaO3,” to be published in Electron. Lett. Google Scholar
- R.C. Alferness and P.S. Cross, “Filter characteristics of codirectionally coupled waveguide with weighted coupling,” IEEE. J. Quantum Electron., vol. QE-14, pp. 843–847, 1978.Google Scholar