A wavelength division multiplexing filter comprises: a first multi-order Mach-Zehnder interferometer comprising a plurality of first-order Mach-Zehnder interferometers, and a second multi-order Mach-Zehnder interferometer comprising a plurality of first-order Mach-Zehnder interferometers; wherein the first multi-order Mach-Zehnder interferometer and the second multi-order Mach-Zehnder interferometer are included in a group of multiple multi-order Mach-Zehnder interferometers arranged within a binary tree arrangement, the binary tree arrangement comprising: a first set of a plurality of multi-order Mach-Zehnder interferometers, the first set including the first multi-order Mach-Zehnder interferometer, and having an associated spectral response with a first spacing between adjacent passbands, and a second set of at least twice as many multi-order Mach-Zehnder interferometers as in the first set, the second set including the second multi-order Mach-Zehnder interferometer, and having an associated spectral response with a second spacing between adjacent passbands that is twice the first spacing.

Aspects described herein include an optical apparatus comprising a plurality of light-carrying media, a wavelength division multiplexing (WDM) device optically coupled with the plurality of light-carrying media, and a lens arranged between the WDM device and a multicore optical fiber. An arrangement of the plurality of light carrying media and the WDM device are selected to align each of the plurality of light-carrying media with a respective optical core of the multicore optical fiber.

Aspects described herein include an optical apparatus comprising a plurality of light-carrying media, a wavelength division multiplexing (WDM) device optically coupled with the plurality of light-carrying media, and a lens arranged between the WDM device and a multicore optical fiber. An arrangement of the plurality of light carrying media and the WDM device are selected to align each of the plurality of light-carrying media with a respective optical core of the multicore optical fiber.

A fiber optic probe is provided with a distal sampling end, a proximal end, and light delivery and collection paths therethrough. The probe includes a window disposed at the distal sampling end of the fiber optic probe, the window having a distal end and a proximal end. A lens is disposed near the proximal end of the window, the lens having a distal end, a proximal end, and an aperture. A light delivery optical fiber is provided having a distal end and a proximal end, the light rays being directed through the aperture. A collection optical fiber is provided in optical communication with the lens and the window. The probe may include a lens collection filter disposed between the window and the lens and an optical isolator provided within the aperture to optically isolate the light delivery path and the light collection path.

A fiber optic probe is provided with a distal sampling end, a proximal end, and light delivery and collection paths therethrough. The probe includes a window disposed at the distal sampling end of the fiber optic probe, the window having a distal end and a proximal end. A lens is disposed near the proximal end of the window, the lens having a distal end, a proximal end, and an aperture. A light delivery optical fiber is provided having a distal end and a proximal end, the light rays being directed through the aperture. A collection optical fiber is provided in optical communication with the lens and the window. The probe may include a lens collection filter disposed between the window and the lens and an optical isolator provided within the aperture to optically isolate the light delivery path and the light collection path.

Aspects described herein include an optical apparatus comprising a plurality of light-carrying media, a wavelength division multiplexing (WDM) device optically coupled with the plurality of light-carrying media, and a lens arranged between the WDM device and a multicore optical fiber. An arrangement of the plurality of light carrying media and the WDM device are selected to align each of the plurality of light-carrying media with a respective optical core of the multicore optical fiber.

A fiber optic probe is provided with a distal sampling end, a proximal end, and light delivery and collection paths therethrough. The probe includes a window disposed at the distal sampling end of the fiber optic probe, the window having a distal end and a proximal end. A lens is disposed at the proximal end of the window, the lens having a distal end, a proximal end, and an aperture. A light delivery optical fiber is provided having a distal end and a proximal end, the distal end being received by the lens aperture. An optical isolator provided within the lens aperture to optically isolate the light delivery path and the light collection path. A collection optical fiber is provided in optical communication with the fiber collection filter. The probe may include a lens collection filter disposed between the window and the lens.

An optical filter system, preferably including an optical input, one or more sets of filters, and/or a control module. A method for optical filter operation, preferably including operating an optical filter system in a normal mode, assessing filter alignment, and/or shifting filter assignments.

In a wavelength selective filter, an optical fiber collimator, an interference filter, and a reflective plate are arranged in this order from front to rear along a z-axis. The collimator has a collimator lens disposed on the rear side of an optical fiber that is opened. The interference filter includes light incident and emitting surfaces, opposed with their xy-planes rotated about a y-axis at a predetermined rotation angle. The reflective plate has a front reflective surface having a normal direction along a z-axis direction, and reflects, toward the front, light incident from the front through the interference filter, to be incident onto the interference filter. The optical fiber collimator causes the input light propagating through the optical fiber from the front to be incident onto the interference filter, and converges the reflected light transmitted through the interference filter to the optical fiber and outputs the light.

An optical fiber having metallic micro/nano-structure on end-facet, and a fabrication method and an application method thereof. The metallic micro/nano-structure is a micro-nano structure resonance cavity on a metallic film, and generates surface plasmon resonance when an optical fiber guided wave is incident. In the fabrication method according to the present invention, the metallic micro/nano-structure on the surface of the substrate is aligned with and is adhered to the end-facet of the optical fiber, and is removed for transferring to the end-facet of the optical fiber. In the application method according to the present invention, the end-facet of the optical fiber is contacted with or moved towards a medium, and a refractive index of the medium is measured by measuring reflection of an optical fiber guided wave by the metallic micro/nano-structure resonance cavity.