OIL’s self-development monomer diffusion technology produces waveguide split junctions that are extremely sharply defined. These sharp splits are possible since no polymer or monomer has to be etched away and removed between the intersecting waveguides These sharp junctions provide for low scatter loss at the junction and the ability to create dense arrays of splitters or combiners when operated in reverse. The product shown here was made for Optelecom, NKF for an Air Force project. This packaged 1 to 16 multimode splitter had the splitter containing film folded in half creating an 8 over 8 configuration enabling connectorization into a standard MT ferrule. Note: The standard MT ferrule form factor can only accommodate 12 fibers, and therefore waveguides, spaced on 250 microns centers. The photo shows the folded splitter with the output ferrule that is packaged into the blue unit using an MPX flexible housing for the MT ferrule output and an FC ferrule for the input. This structure ensures no mechanical or thermal stress on the PWG splitter inside the package.
As note in the above, OIL’s PWG technology enables extremely sharp junctions which with some waveguide design modifications create efficient low loss combiners. Hundreds of 4 to 1 and 8 to 1 combiners where made for OptiComp Corp., now Zephyr Photonics, for use in a wavelength combining capability. Show in the photo is an 8 to 1 combiner inserted into Zephyr Photonics package mounted on a circuit board. Six different wavelengths of light were coupled into the device with the single fiber output containing all 6 wavelengths that are displayed in the photo. Coupling efficiency was excellent. The splitter/combiner design work well in both splitting and combining operations.
OIL’s Star Couplers (Signal Mixing and Distribution, and Novel Splitting): Multiple low loss splitting junctions enable creation of N by M star couplers for uniform signal distribution to be created. Shown is a connectorized 8x8 star coupler not shown packaged. The design concept enables 1 to M splitting that is not restricted to even numbers as with conventional tree branch splitting. Thus N and M can each take on a range of both identical and non-identical integers. Internal imaged mode scramblers can be used to ensure balanced performance regardless of input modal distribution.
As Data Centers begin to convert to optical interconnections signal monitoring taps are needed to determine signal fidelity. Thus there is a growing need for compact small footprint packaged tap monitoring units that operate with low loss and good stable balance independent of modal content of the input signals. OIL has developed dense splitter arrays to achieve these requirements. Evaluation units have been designed for and sold to a confidential customer (under an NDA). Final optimization to meet loss and network requirements is nearly complete. The photo shows a silicon wafer encapsulated bi-directional array of splitters with input and output ports all on 250 microns centers. Bi-directionality refers to having alternating splitter directions to minimize the package footprint. 30 by 30 port units with 10 interleaved splitters have been constructed in a 1.2 cm by 0.6 cm footprint. Fiber array connectors are shown with alignment pins to facilitate interconnection for the network and monitor channels. See the next photo for the splitter array layout with internal mode scramblers.
OIL’s interleaved bi-directional 1 to 2 splitter layout for network taps: As per the previous photo description the bi-directional waveguide splitter arrangement creates the smallest compact footprint. OIL’s unique capability and design for mode scramblers that are imaged during waveguide exposure is shown with the two stage units at each larger input waveguide. This ensures that over a wide range of modal inputs that the splitters will remain balanced for the specific design. Currently we have designs for signal channel to tap channel ratios of 50/50, 70/30, and 60/40. Balance ratios are within 5% ie 53 to 47 etc. More detail is provided in the product prototype capability section below as well as at #10 ref.
OIL’s mode stabilized 1x4 splitter for NASA satellite system calibration testing: 1 to 4 splitters were designed and delivered to Fibertek to meet rigorous output channel to channel signal power stability requirements over low (pico watts) to high (100’s of milli-watts) power input relative to varying modal inputs. The splitters were used by NASA’s ICESat2 project for laboratory calibration of their satellite system to ensure against power and thermal induced modal variations producing power per channel drift between the 4 outputs. Pulsed lasers at 1098nm are used in the system. Internal mode scramblers were imaged during OIL’s waveguide exposure into the input waveguide located at the white dot on the right in the photo. The scramblers act as low refractive index deflectors that preferentially deflect low angle modes to higher (angle) modes to ensure mode fill is at a reasonable fill or in other words meeting encircled flux conditions. Balanced stable splitting requires this level of mode fill. The units were fully packaged as shown. Fibertek commented that they were “very impressed by (our) superior performance, very low insertion loss and stable split-ratio (control) over varying (power level induced) input modal distributions”. Additionally they noted that fused fiber splitters with conventional mode scramblers did not meet their requirements.