Wavesplitter Technologies, Inc.

Joseph C Chon

Chi-hung Huang

Huali Ariel Luo

Robert Huang

Wayne Liao

Sheau Sheng Chen

Jerry R Bautista

Weilong William Lee

Chiahung Chiu

Sheau-Sheng Chen

A method and apparatus is provided for biasing an avalanche photodiodes (APD). The method includes developing a first output signal s(v) from the APD when biased with a first bias voltage vand developing a second output signal s(v) from the APD when biased with a second bias voltage v, wherein s(v)=PRZM(v), (P) is an light power illuminating the APD, R is a responsivity of the APD, M(v) is an APD avalanche gain and Z is a trans-impedance amplifier gain (Z). The method continues by acquiring a ratio r=s(v)/s(v)=PRZM(v)/[PRZM(v)]=M(v)/M(v) and invoking a feedback control method to bias the APD using the ratio r.

Method and apparatus for controlling the gain of an avalanche photodiode with fluctuations in temperature

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

An optical add/drop filter (OADF) module is provided that is capable of only utilizing one filter to drop and add multiple channels from a multiplexed signal. In one embodiment, a demultiplexer separates the input signal into groups of signals or channels to be dropped. This group of channels is coupled to one input of a 2&times;2 interleaving OADF, which in one embodiment is an unbalanced Mach-Zehnder Interferometer, while another group of channels to be added back to the multiplexed signal is coupled to the other input. One output of the OADF drops one group of channels, while the other output transmits the added group of channels to an input of a multiplexer, which combines the group of added channels with the other groups of channels from the outputs of the demultiplexer. In another embodiment, a multi-window filter formed from an unbalanced Michelson Interferometer outputs two signals, each having either odd or even wavelength signal components. The signal to be dropped is input back to an optical circulator, which drops the signal from an exit port. The other signal is input to a second optical circulator, which combines the two signals into a single signal with both even and odd wavelength signals. Consequently, large numbers of channels can be dropped and added using only a single filter, thereby reducing leakage loss due to propagation through multiple filters.

Expandable interleaving optical add/drop filter module

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

Joseph C Chon