Abstract: Techniques for designing optical devices with high isolation are disclosed. The high isolation is achieved by causing a reflected light signal to go through another filter. According to one embodiment, an optical apparatus comprises a first optical filter configured to transmit a first selected wavelength and reflect all other wavelengths, a second optical filter the second optical filter configured to transmit a second selected wavelength and reflect all other wavelengths. The first optical filter, being not perfect and producing a reflected signal with a residual of a signal at the first selected wavelength, the residual of the signal is minimized by the second optical filter when the reflected signal is impinged upon the second optical filter.

Abstract: Techniques for designing optical devices with passive components for erbium and other doped fiber amplifiers are disclosed. In one aspect, all passive components needed to construct optical amplifiers of both single and multiple-stage forward or backward pumps are integrated without extensively using optical fiber splicing joints. One of the features is to use free-space optics for inter-function cascades among various necessary functions, such as one or more tap couplings, WDM filtering to multiplex (Mux) or de-multiplex (Demux) pump and signal lights, gain-flattening, pump isolation and even performing Mux and Demux of different polarizations.

Abstract: Techniques for designing optical devices that can be manufactured in volume are disclosed. An optical assembly is build individually and includes a first tube with one end being polished to a slanted angle and attached with a filter. Because of the slanted angle, a predefined angle of incidence can be defined. The assembly is then bonded to a substrate on which other components or more such assemblies are bonded to form an integrated piece. Depending on implementation, the first tube may include no other element, a lens, or a lens and a fiber pigtail that are encapsulated. In the case that the first tube includes no other element or only a lens, a second tube is provided to include a fiber pigtail and a lens, or simply a fiber pigtail. One of the advantages of having two tubes is the underlying mechanism providing a lateral adjustment between the two tubes.

Abstract: Optical apparatus for combining and splitting optical signals using folded waveguides and method for making the same are disclosed. According to one aspect of the present invention, at least one waveguide used in the optical apparatus is folded around according to a predefined curve to couple to other waveguides. The predefined curve is so designed as to minimize possible insertion loss as a result of such folding of the waveguide. The proper folding of the waveguide leads to modified designs of the optical devices with all the ports on one side so as to simplify the alignment procedures afterward. In addition, the optical device according to the present invention has much smaller footprint and makes it possible to increase higher yield from fabricating substrate material on which the waveguides are formed.