We present the design, fabrication and characterization of efficient fiber-to-chip grating couplers on a Germanium-on-Silicon (Ge-on-Si) and Germanium-on-silicon-on-insulator (Ge-on-SOI) platform in the 5 µm wavelength range. The best grating couplers on Ge-on-Si and Ge-on-SOI have simulated coupling efficiencies of -4 dB (40%) with a 3 dB bandwidth of 180 nm and -1.5 dB (70%) with a 3 dB bandw...

Fused fiber components are the key building blocks that enable reliable and efficient operation of high power fiber lasers. In this paper, we review fabrication techniques for the manufacture of such devices, including mode-field adaptors, fiber tapers, fused couplers, and fused combiners. We present the basic equations governing both the optical performance and fabrication requirements for the...

A new model is presented for a step-index fiber in the form of an equivalent slab guiding structure. This model simplifies the analysis of fiber directional couplers and coupler half-blocks with dielectric and metallic superstrates. Simple empirical formulas to obtain the model parameters are also given. The use of this model is illustrated with some numerical examples.

Mode division multiplexed optical transmission enabled by all-fiber mode multiplexer is investigated. The proposed all-fiber mode multiplexer is composed of consecutive mode selective couplers. It multiplexes or demultiplexes LP01, LP11, LP21, and LP02 modes simultaneously. We demonstrate successful transmission of three spatial modes with 120 Gb/s PDM-QPSK signals over 15 km of four mode fiber...

We demonstrate a compact, fiber-pigtailed, 4-by-4 wavelength router in Silicon-on-insulator photonic wires, fabricated using CMOS processing methods. The core is an AWG with a 250GHz channel spacing and 1THz free spectral range, on a 425x155 microm(2) footprint. The insertion loss of the AWG was reduced to 3.5dB by applying a two-step processing technique. The crosstalk is -12dB. The device was...

The paper reviews the recent progress on CO2-laser writing of long-period fiber gratings (LPFGs) in different kinds of fibers, including conventional single-mode fiber (SMF), boron-doped SMF, polarization-maintaining fiber, photonic crystal fiber, and polarization-maintaining photonic crystal fiber. In particular, we report the writing dynamics for the understanding of the physical mechanisms i...

We demonstrate fully-etched fiber-waveguide grating couplers with sub-wavelength gratings showing high coupling efficiency as well as low back reflections for both transverse electric (TE) and transverse magnetic (TM) modes. The power reflection coefficients for the TE and TM modes have been significantly suppressed to -16.2 dB and -20.8 dB, respectively. Focusing grating lines have also been u...

We report on the design and fabrication of compact and potentially low-cost multimode fiber matched 1 x N and N x N couplers for LAN’s. The design utilizes the self-imaging effect and tapering of the Multi-Mode Interference (MMI) section. An extended mode propagation analysis and 3-D beam propagation method (BPM) were used to analyze and design these structures. The simulations show that the co...

We report an all-fiber mode division multiplexer formed with cascaded mode selective couplers with significantly broadened bandwidth potentially spanning S, C and L band. This was achieved by matching the effective refractive indices over a wide wavelength range for the few mode fiber and the single mode fiber used in the coupler. The multiplexer provides high coupling efficiency (>55% for the ...