Optical Trapping using a Lensed Multicore Fiber

Research on fusion splicing technology of 7-core fiber

Two dimensional trapping of multiple particles in an interference pattern has been demonstrated using a four core lensed multicore fiber and a diffractive optical element.

Using a fusion splicer, we demonstrate tapered core expansion at the facet of a custom visible-light 16-core fiber. Across all cores, the average mode-field diameter was expanded from 3.1µm to 8.9µm at λ=488nm.

Multi-core fiber (MCF) has been one of the main innovations in fiber optics in the last decade. Reported work on MCF has been focused on increasing the transmission capacity of optical communication links by exploiting space-division multiplexing. Additionally, MCF presents a strong potential in optical beamforming networks. The use of MCF can increase the compactness of the broadband antenna array controller. This is of utmost importance in platforms where size and weight are critical parameters such as communications satellites and airplanes. Here, an optical beamforming architecture that exploits the space-division capacity of MCF to implement compact optical beamforming networks is proposed, being a new application field for MCF. The experimental demonstration of this system using a 4-core MCF that controls a four-element antenna array is reported. An analysis of the impact of MCF on the performance of antenna arrays is presented. The analysis indicates that the main limitation comes from the relatively high insertion loss in the MCF fan-in and fan-out devices, which leads to angle dependent losses which can be mitigated by using fixed optical attenuators or a photonic lantern to reduce MCF insertion loss. The crosstalk requirements are also experimentally evaluated for the proposed MCF-based architecture. The potential signal impairment in the beamforming network is analytically evaluated, being of special importance when MCF with a large number of cores is considered. Finally, the optimization of the proposed MCF-based beamforming network is addressed targeting the scalability to large arrays.

We describe a new multicore fiber (MCF) receptacle for space division multiplexing (SDM) based transceiver applications, in which we integrated a compact fiber-bundle type fan-in/fan-out device for directly connecting MCF to LDs and PDs. We design the length of the fan-out fibers taking their bending stress into account to achieve a configuration with a smaller footprint. With the proposed receptacle, we develop a 100 Gb/s SDM transmitter based on a four-channel, 1.3 μm membrane laser array on Si, in which spot-size convertor (SSC) using inverse taper InP and SiON waveguides is integrated. Since the core size of SiON waveguide is much smaller than that of MCF, we utilize different fibers with optimized modal fields at each connection point and introduce thermally-expanded-core (TEC) fusion splicing to realize a low-loss connection between them. We achieve a pluggable connection between the lasers and 125 μm-cladding 4-core MCF in an LC connector. The developed receptacle maintained satisfactory laser characteristics including sufficient output power and clear eye openings for directly modulated 28 Gb/s NRZ signals. We also achieve an error-free transmission at a bit-error rate of less than 10−12 with a 500-m MCF transmission link for all 4 channels with simultaneous 4-channel operation.

An all-fiber approach is utilized to phase lock and select the in-phase supermode of compact multicore fiber lasers. Based on the principles of Talbot imaging and waveguide multimode interference, the fundamental supermode is selectively excited within a completely monolithic fiber device. The all-fiber device is constructed by simply fusion splicing passive non-core optical fibers of controlled lengths at both ends of a piece of multicore fiber. Experimental results upon in-house-made 19- and 37-core fibers are demonstrated, which generate output beams with high-brightness far-field intensity distributions. The whole fabricated multicore fiber laser device can in principle be a single fiber chain that is only ~10 cm in length, aligning-free in operation, and robust against environmental disturbance. Keywords: fiber laser, multicore fiber, phase-locked oper ation, Talbot imaging, multimode interference 1. INTRODUCTION Multicore fiber (MCF) with doped core array has been recen tly developed and it brings a promising solution to power-scalable fiber lasers of short length.

A pair of compact fan-in and fan-out device is developed that connects 7-core multi-core fiber and seven single mode fibers. Insertion loss is below 0.6 dB. Polarization dependent loss less than 0.1 dB (@1550 nm), and cross talk better than -50 dB (@1550 nm) are realized.

In-line Mach-Zehnder interferometer for simultaneous measurement of temperature and directional torsion

We designed and fabricated all-fiber fan-in/fan-out (FI/FO) devices using a fused taper technique for square lattice structure coupled-core multicore fiber (CC-MCF). A vanishing core bridge fiber with a diameter of 80 μm was tailor-designed to minimize both the mode field mismatch and the required tapering ratio at the same time. In experiment, we succeeded in fabricating FI/FO devices with a core pitch as small as 17 μm and achieving practically low insertion losses of 1.43 dB and 2.28 dB for fan-in and fan-out devices, respectively. The fabricated FI/FO devices can well multiplex and demultiplex 1550 nm light into and out from the CC-MCF without obvious total power fluctuation even when an external perturbation is intentionally imposed on the CC-MCF. The proposed FI/FO device is very useful for both the study and application of CC-MCFs which usually have ultra-small core pitches.

We design and fabricate a multicore fiber sensor with the end facets of cores patterned with one-dimensional sub-wavelength Au wire grid polarizers, which are aligned either radially or azimuthally on the cross section of the fiber. With a fan-out device bridging the individual cores and external single core fibers followed by a compact spectrometer, it is able to spatially detect the light intensity, spectrum, and polarization states of the incident light in a highly integrated format. These multicore fiber sensors offer a new opportunity to simultaneously measure multiple optical parameters by a single operation.

A cable link with 288 four-core multicore fibers and 288 pairs of fanout devices was deployed in the field and its losses were evaluated. No excess losses were observed from MCF-related components in field installation.

Fan-out device for multicore fiber coupling application based on capillary bridge self-assembly fabrication method

A multicore all-fiber probe is demonstrated that has been fabricated using an electric arc fusion splicer. Interference of the fiber output when coherent light is coupled into two cores is investigated. The properties of the fringes created when the fiber is probing different media were found to be in general agreement with a beam propagation method simulation. Optical manipulation of microspheres near to the end of the probe is examined and the potential for controlled trapping explored. Polymer microspheres with diameters of 2 microns were formed into regular patterns due to the presence of the interference fringes.