Wavesplitter Technologies, Inc.

Chi-hung Huang

Joseph C Chon

Robert Huang

Huali Ariel Luo

Sheau Sheng Chen

A structure and method are provided to improve stability of a multi-window dense wavelength division multiplexers and to provide polarization-independent multi-window dense wavelength division multiplexers. In one embodiment, the coupler region of a multi-window wavelength division multiplexer (MWDM) is hermetically sealed in a protective casing to prevent moisture from affecting the passband wavelength drifting in the coupler. In one embodiment, the coupler is elastically twisted at the fused fiber portion to reach polarization cancellation. In another embodiment, the coupling region of the coupler is exposed to UV-radiation for passband wavelength adjustment. In yet another embodiment, a passive thermal compensation technique is used to minimize the thermal effect on the passband wavelengths for dense WDM applications. In a further embodiment, the coupler is mounted on the substrate using soft adhesives in conjunction with rigid adhesives, to improve mechanical shock protection.

Polarization-independent, environmentally stable optical fiber narrow band multi-window wavelength division multiplexer based on biconical tapered fusion coupler technology

A fused-fiber multi-window wavelength filter (MWF) is constructed with an unbalanced Michelson Interferometer, in which input light passing through the fused coupling region is decoupled and travels along two fibers of different optical path lengths. The two light signals travel to the end of the two fibers, where a highly reflective coating reflects the light back toward the coupling region, where the signals are coupled again and then decoupled after exiting the coupling region. By adjusting the optical path length difference, either by changing the length or refractive index, a signal at a desired wavelength can be obtained at the filter output. The MWF can be combined with other MWFs to form more compact sized multi-window wavelength division multiplexers (MWDMs) and dense WDMs. Passive thermal compensation techniques can be applied to one or both of the reflecting fibers to maintain the desired optical path length difference.

Fused-fiber multi-window wavelength filter using unbalanced Michelson Interferometer

According to the present invention, a multi-window wavelength division multiplexer (MWDM) is coupled to a correcting filter characterized by a shallow modulation depth and a channel separation smaller than the MWDM. A correcting filter is coupled to an input of the MWDM or to each of the two outputs of the MWDM. By changing the modulation depth and/or channel separation of the correcting filter(s), the spectral response of the filter can be adjusted to produce a more uniform gain (i.e., a &ldquo;flat-top&rdquo; spectral response) across wavelengths of passbands within the MWDM. In one embodiment, the correcting filter is an unbalanced Mach-Zehnder interferometer formed with two fused-fiber couplers having non-equal splitting ratios. In other embodiments, the correcting filter is a Fabry-Perot interferometer having a low end-face reflectivity.

Fiber unbalanced Mach-Zehnder interferometers with flat-top spectral response for application in wavelength division multiplexers

A wavelength division multiplexer (WDM) utilizes cascaded interferometric devices, where the two output branches of interferometric devices in each new stage are each coupled to an additional stage of interferometric devices having the same wavelength separation or channel spacing, which suppresses the sidelobes of the signals from preceding stage of interferometric devices. In one embodiment, the interferometric devices are unbalanced Mach-Zehnder Interferometers.

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Fremont, CA, United States of America

Chi-hung Huang