Disclosed is a compact device for wavelength-division multiplexing applications. In particular, disclosed is a device that includes a housing and a core at least partially positioned within the housing. The core includes a first single fiber stub, a second single fiber stub, and at least one functional layer positioned between a first fiber of the first single fiber stub and a second fiber of the second single fiber stub. The at least one functional layer is configured to: (i) permit routing of a transmission signal of a multiplexed signal along an optical path from the first fiber stub to the second fiber stub, and (ii) prevent routing of a non-transmission signal of the multiplexed signal along the optical path from the first fiber stub to the second fiber stub. A distance between a first ferrule of the first fiber stub and a second ferrule of the second fiber stub is less than about 0.05 mm.

Disclosed is a compact device for wavelength-division multiplexing applications. In particular, disclosed is a device that includes a housing and a core at least partially positioned within the housing. The core includes a first single fiber stub, a second single fiber stub, and at least one functional layer positioned between a first fiber of the first single fiber stub and a second fiber of the second single fiber stub. The at least one functional layer is configured to: (i) permit routing of a transmission signal of a multiplexed signal along an optical path from the first fiber stub to the second fiber stub, and (ii) prevent routing of a non-transmission signal of the multiplexed signal along the optical path from the first fiber stub to the second fiber stub. A distance between a first ferrule of the first fiber stub and a second ferrule of the second fiber stub is less than about 0.05 mm.

An optical resonator (100) comprises an optical waveguide device (10) having an optical axis (OA) and extending with a longitudinal length between two waveguide end facets (11), resonator mirrors (13) being arranged for enclosing a resonator section (14) of the optical waveguide device (10), and a ferrule (20) having two ferrule facets (21), wherein the optical waveguide device (10) is mounted to the ferrule (20) and the ferrule (20) extends along the full longitudinal length of optical waveguide device (10). Furthermore, an optical apparatus (200) including the optical resonator (100) and a method of manufacturing the optical resonator (100) are described.

An output coupler can be used to couple multiple channels of light from a semiconductor waveguide to an optical fiber for wavelength division multiplexing. To couple light of a wide bandwidth (e.g., equal to or greater than 100 nm), two symmetrical gratings on two sides of a Fabry Perot cavity is used. The two symmetrical gratings are optimized to both reflect light for a Fabry Perot resonator and couple light out of the semiconductor waveguide.

In some implementations, an optical assembly includes a first etalon, a second etalon, and an optical element disposed between the first etalon and the second etalon. The first etalon is configured to transmit a collimated light beam from an input surface of the first etalon to an output surface of the first etalon, and to allow the collimated light beam to propagate from an output surface of the first etalon to the optical element. The optical element is configured to receive the collimated light beam, to change the collimated light beam to a de-collimated light beam, and to allow the de-collimated light beam to propagate from the optical element to an input surface of the second etalon. The second etalon is configured to transmit the de-collimated light beam from the input surface of the second etalon to an output surface of the second etalon.

A reflective structure includes an input/output port and an optical splitter coupled to the input/output port. The optical splitter has a first branch and a second branch. The reflective structure also includes a first resonant cavity optically coupled to the first branch of the optical splitter. The first resonant cavity comprises a first set of reflectors and a first waveguide region disposed between the first set of reflectors. The reflective structures further includes a second resonant cavity optically coupled to the second branch of the optical splitter. The second resonant cavity comprises a second set of reflectors and a second waveguide region disposed between the second set of reflectors.

Embodiments relate to an optical sensor for sensing hydrogen gas, which includes an optical fiber through which light moves; a ferrule formed at one end of the optical fiber to surround the optical fiber; and a sensor module configured to form an interference wave according to a Fabry-Perot interferometer with respect to light that moves through the optical fiber, wherein the sensor module includes a sensing material that expands and contracts by reacting with hydrogen gas, and spectrum periodicity of the interference wave changes according to a volume change of the sensing material, and a hydrogen gas detection system including the optical sensor.

An external resonator type light-emitting device includes a light source oscillating a semiconductor laser light and a grating element configuring an external resonator together with the light source. The light source includes an active layer oscillating the semiconductor laser light. The grating element includes an optical waveguide and a plurality of Bragg gratings formed in the optical waveguide. The optical waveguide includes an incident face on which the semiconductor laser light is incident and an emitting face from which an emitting light having a desired wavelength is emitted.

A reflective structure includes an input/output port and an optical splitter coupled to the input/output port. The optical splitter has a first branch and a second branch. The reflective structure also includes a first resonant cavity optically coupled to the first branch of the optical splitter. The first resonant cavity comprises a first set of reflectors and a first waveguide region disposed between the first set of reflectors. The reflective structures further includes a second resonant cavity optically coupled to the second branch of the optical splitter. The second resonant cavity comprises a second set of reflectors and a second waveguide region disposed between the second set of reflectors.

A fiber optic sensor, a process for utilizing a fiber optic sensor, and a process for fabricating a fiber optic sensor are described, where a double-side-polished silicon pillar is attached to an optical fiber tip and forms a Fabry-Prot cavity. In an implementation, a fiber optic sensor in accordance with an exemplary embodiment includes an optical fiber configured to be coupled to a light source and a spectrometer; and a single silicon layer or multiple silicon layers disposed on an end face of the optical fiber, where each of the silicon layer(s) defines a Fabry-Prot interferometer, and where the sensor head reflects light from the light source to the spectrometer. In some implementations, the fiber optic sensor may include the light source coupled to the optical fiber; a spectrometer coupled to the optical fiber; and a controller coupled to the high speed spectrometer.