Optical: systems and elements – Polarization without modulation – By relatively adjustable superimposed or in series polarizers
Reexamination Certificate
2001-11-26
2004-09-21
Lavarias, Arnel C. (Department: 2872)
Optical: systems and elements
Polarization without modulation
By relatively adjustable superimposed or in series polarizers
C359S484010, C359S281000, C385S011000
Reexamination Certificate
active
06795245
ABSTRACT:
BACKGROUND OF THE INVENTION
Optic switches are indispensable in future all-optical broadband telecommunication systems. The current optical switches include optical mechanical switches (OMS) including MEMS, thermooptic switches (TOS); liquid crystal switches (LCS) and electro-optic switches (EOS). The drawback of OMS/MEMS, TOS and LCS are their low speed (switching time ~10 ms or longer) and poor mechanical reliability. Although EQS is fast (switching speed can be a few nano-seconds), its complicated fabrication process, polarization dependence and huge optical insertion loss limit its applications.
The magnetooptic switches in accordance with the present invention are based on light polarization manipulation using Faraday rotators and polarization beam splitters/combiners, and will not have the above drawbacks.
SUMMARY OF THE INVENTION
The magnetooptic switches (MOS) in accordance with the present invention are based on magnetooptic effects in Faraday rotators. In particular, switching Faraday rotators are utilized in combination with polarization beam splitters/combiners (PBS) and walk-off plates. The mechanism of the magnetooptic switches is based on light polarization manipulation. The Faraday rotators are Bi-substituted magnetic garnets with small saturation fields, and the PBS is made from birefringence crystals (such as TiO2, YVO4, . . . ). The switching Faraday rotator is mounted inside a magnetically soft ferrite core, which is magnetized by an electric coil surrounding the ferrite core when an electrical current is applied to the electric coil. To ensure high switching speed, the ferrite core is selected to exhibit high frequency (>10 MHz) characteristics. When a magnetic field is generated by the electric current in the coil, the ferrite core will be magnetized to produce a magnetic field large enough to switch the Faraday rotator, which, in turn, changes the polarization rotation of the linearly polarized lights. Based on the same principle of polarization manipulation, a latching magnetooptic switch (only a current pulse is required) can be built using a latchable Faraday rotator as a switching control unit. The magnetooptic switch can be either a transmissive or reflective type. The advantage of a reflective-type switch is the fact that less optical parts are needed and also a leak portion can be used as a monitoring signal. The advantages of these magnetooptic switches include: high speed (~&mgr;s or faster), low insertion loss, low polarization dependent loss (PDL) and polarization mode dispersion (PMD), compactness in size, no moving parts, and no liquid and organic materials in the optical path.
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Lavarias Arnel C.
Sawyer Law Group LLP
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