Single Aperture Multiple Optical Waveguide Transceiver
A single-aperture, multi-axial transceiver is provided that is particularly useful in a LIDAR system for detecting low velocities at increased ranges. The system is particularly useful in systems that measure very low velocities and very short distances as well as to provide an operating range of hundreds of meters. The transceiver uses closely spaced waveguides placed near the focal point of a single objective to form input and detector apertures.
1 . A method, comprising:
securing a first optical fiber, having a core and a cladding, in a first v-groove to thereby form a first fiber-in-groove assembly;
securing a second optical fiber, having a core and cladding, in a second v-groove to thereby form a second fiber-in-groove assembly;
polishing, machining, or etching, the respective claddings of the first and second optical fibers to thereby generate respective first and second flat polished surfaces on the first and second optical fibers; and
bonding the first and second fiber-in-groove assemblies together such that the respective first and second flat polished surfaces are facing one another to thereby foam a dual waveguide structure,
wherein a distance between the cores of the first and second optical fibers is less than half the sum of a cladding diameter of the first optical fiber and a cladding diameter of the second optical fiber.
2 . The method of claim 1 , wherein the securing is performed using silicon v-grooves.
3 . The method of claim 1 , wherein the first and second optical fibers have cladding diameters between 80-125 microns.
4 . The method of claim 1 , wherein:
The distance between the cores of the first and second optical fibers is less than 80 microns.
5 . The method of claim 1 , wherein:
the distance between the cores of the first and second optical fibers is less than about 30 microns.
6 . The method of claim 1 , wherein:
the distance between the cores of the first and second optical fibers is less than about twenty wavelengths.
7 . The method of claim 1 , wherein the dual waveguide structure propagates light having wavelength of about 1550 nm.
8 . The method of claim 1 , wherein:
the bonding is performed such that a dual waveguide structure is formed having an air gap between the respective first and second flat polished surfaces.
9 . The method of claim 1 , wherein:
the bonding further comprises using spacer elements having a low coefficient of thermal expansion to thereby form an air gap between the respective first and second flat polished surfaces that is substantially insensitive to temperature.
10 . The method of claim 1 , wherein:
the bonding further comprises using spacer elements each having a different coefficient of thermal expansion than that of the v-grooves to thereby form an air gap between the respective first and second flat polished surfaces, and
respective lengths of the spacer elements and the v-grooves are configured such that the air gap is substantially insensitive to temperature.
11 . The method of claim 1 , further comprising:
forming a gap between the respective first and second flat polished surfaces that is filled with a material that is opaque or has a lower index of refraction than that of the optical fibers.
12 . The method of claim 1 , further comprisuing:
forming a gap between the respective first and second flat polished surfaces that is filled with a thin metal film.
13 . A method, comprising:
etching a plurality of optical fibers, each having a core and a cladding, to thereby reduce a cladding diameter of each of the plurality of optical fiber from an initial cladding diameter to a reduced cladding diameter;
metallizing each of the etched plurality of optical fibers;
bundling the plurality of optical fibers into a ferrule;
bonding the bundle with an adhesive or opaque material to form a composite structure;
trimming excess fiber to a surface of the ferrule, to thereby generate a surface of the composite structure;
polishing the surface of the composite structure to thereby form a waveguide structure,
wherein at least one distance between the cores of first and second ones of the plurality of optical fibers is less than half the sum of an initial cladding diameter of the first optical fiber and an initial cladding diameter of the second optical fiber.
14 . The method of claim 13 , wherein:
at least one distance between cores of the first and second ones of the plurality of optical fibers is less than 80 microns.
15 . The method of claim 13 , wherein:
at least one distance between the cores of the first and second ones of the plurality of optical fibers is less than about 30 microns.
16 . The method of claim 13 , at least one distance between the cores of the first and second ones of the plurality of optical fibers is less than about twenty wavelengths.
17 . The method of claim 13 , wherein the waveguide structure propagates light having wavelength of about 1550 nm.
18 . A method comprising:
assembling optical fibers into a bundle;
heating the bundle until the optical fibers are softened;
mechanically pulling the bundle to fuse a portion of the optical fibers into a composite structure;
mechanically cleaving the fused portion of the composite structure to generate a waveguide structure.