Multi-fiber Connectors Research Articles

Mechanical performance of physical-contact, multi-fiber optical connectors: Finite element analysis and semi-analytical model

Abstract Three-dimensional finite element analysis of physical-contact, multi-fiber optical connector was used to characterize fiber-to-fiber contact and support the development and validation of a semi-analytical model (SAM) for the contact force. This contact behavior is determined by the elastic deformation of the system components (ferrule, fibers, and bonding adhesive) and the classical Hertzian contact at the fiber tips – effects that ultimately define the axial compliance of the system. Two 3-D finite element models for a 12-fiber connector are constructed to study the contact of two connectors, and the specific numerical simulations are carried out to generate input data to SAM, confirm the main assumptions made in its development, and numerically validate the predictions for the contact force. These simulations mainly consider non-uniform fiber height profiles and different end-face fiber tip geometries characterized by their radius of curvature. The numerically validated SAM is then used to study some performance aspects of multi-fiber connectors as related to the required contact force, namely, finding fiber height profiles that require minimum contact force and evaluating the throughput of polishing processes assuming a target contact force. Predictions are supported by Monte Carlo simulations and associated with current profile geometry metrics.

Optimum design for the contact surface of multifiber optical connectors

The core diameter of a single-mode fiber is about 8 to 10µm. Any slight misalignment or deformation of the optical mechanism will cause significant optical losses at connections. Previous studies have concentrated on improving the manufacturing process to obtain high-precision components. Although the precision can be controlled, misalignment may still occur owing to the contact stress on the connecting interface. This study used the finite-element method to simulate the contact status, and used MT-series connectors as examples. The connectors use a guide-pin structure to align the two contact surfaces, and use a spring or clip to maintain tight contact. Because the MT ferrules are made of plastic materials, they are softer than ceramic ones and the deformation strains are more significant. For the finite-element analysis, a solid model of the MT ferrule with a convex end, oblique angle, and fiber protrusion can be constructed according to the JIS C5981 standard. Results of a simulation, integrating the optimization technique and ANSYS software, showed that the fiber center displacement for the commonly used oblique PC connectors would be 0.9 µm. This will significantly affect the eccentricity tolerances for single-mode applications, because a maximum of 1.5 µm is acceptable. Using the resulting new standard (eccentricity <0.6 µm) to select ferrules, and making them into connectors, it is found that the insertion losses in 98% of connectors are less than 0.3 dB. This result satisfies the requirement for single-mode applications.

Compact 90$^{\circ}$ Releasable Multifiber Optical Connectivity Solution

A compact releasable 90deg optical connectivity solution is proposed, realized, and characterized. It can be used for angled interconnection between two small form factor multifiber connectors, or between one connector and surface mounted multichannel active optical elements such as vertical-cavity surface-emitting lasers and photodetector arrays. This 90deg connectivity system is based on V-groove substrates and an integrated optical microsystem combining two lens arrays and a 45deg mirror. Realized modules feature average fiber-to-fiber optical losses of 1.4 dB (best below 1 dB) for multimode operation over the whole wavelength range from 850 up to 1550 nm. This interconnect solution provides advantages when limited space is available (e.g., in optical distribution frames, splice closures, high-performance computers)

Design and performance of very high-density multifiber connectors employing monolithic 60-fiber ferrules

High-density high-count mechanically transferable (MT) type and multifiber push-on (MPG) type connectors were constructed by using a monolithic 60-fiber ferrule which aligns five stacked 12-fiber ribbons. The connectors have a high packaging density of 286 fibers/cm/sup 2/ for the MT type and 40 fibers/cm/sup 2/ for the MPO type. We fabricated both types of 60-fiber connector. The average insertion loss of the MT type was 0.20 dB with index-matching and that of the MPO type was 0.70 dB without index-matching.

SC-DC/SC-QC fiber optic connector

The SC-DC™ and SC-QC™ (SC-DC/SC-QC are registered trademarks of Siecor) are multifiber optical connectors for conventional optical network applications. The SC-DC and SC-QC connectors were designed to provide a new interface technology that is significantly smaller than the duplex SC interface. The small SC-DC and SC-QC connector interfaces occupy half the space of an SC connector, effectively doubling the number of fiber ports in a given space. In addition, SC-DC and SC-QC connectors are simpler to install as well as offering greater packing density for both electronics and cable management. The connector design and performance of the SC-DC/SC-QC connector for both single-mode and multimode applications are described.

Photonic packaging using laser/receiver arrays and flexible optical circuits

Optoelectronic modules and multifiber optical connectors were successfully applied to intrasystem interconnection within a large telecommunication transmission terminal. The optoelectronic modules are 32-channel 850 nm vertical cavity surface emitting laser (VCSEL) and detector arrays packaged using multichip module technology system components include multimode silica optical fibers and silicon V-groove technology based multifiber optical connectors. The system architecture presented particularly difficult challenges for parallel optics because of complex cable assemblies required by the fan-out nature of the cables and the signal bifurcation needed to accomplish duplication, Nevertheless, the experiments completed demonstrate that parallel optics can dramatically increase the capacity of telecommunications equipment with no significant changes in system or physical architecture. The density of the optical modules and connectors clearly demonstrates that optical interconnection technology will be able to support the input/output (I/O) requirements of new generations of integrated circuit technology.

Clamp spring removal and fitting method for optical multifiber connector with index matching material

In single-mode multifiber connectors, the ferrule endfaces spacing is filled with index matching material and the contact is pushed by the clamp spring. To perform the transfer splicing, the clamp spring must be removed and fitted before and after the transfer action. In this paper, first, the relations among the ferrule pushing force, Young's modulus of the ferrule material, radii of curvature of ferrule endfaces, contact length, etc., are investigated elastomechanically to find the conditions under which the ferrule endfaces-contact remains stable. Next, the fluidity of index matching material and the applied force, together with loss variations are investigated to clarify the mechanisms responsible for loss generation and the situation in which the losses can be kept small. Finally, based on the results of these investigations, the removable clamp spring and fitting mechanism is manufactured. By evaluation of its characteristics, it is shown that satisfactorily good performances are confirmed.

Connection loss reduction by thermally-diffused expanded core fiber

Connection loss reduction in ten fiber connectors prepared by the thermally diffused expanded core (TEC) method has been confirmed. The mode field diameters (MFDs) of conventional single mode (SM) fibers were expanded from 9.8 to 13 mu m by thermal treatment considering the influence of loss increase due to fiber axis misalignment. An average connection loss of 0.15 dB for 4-SM-fiber connectors was realized, which was improved by 0.22 dB compared with previous value of 0.37 dB without thermal treatment. The TEC method promises to reduce the coupling loss, which is caused by lateral offset of multifiber connectors, fiber/LD modules, and fiber/waveguide device modules. >

Optical-fiber fanout connector for 10-fiber ribbon cable termination

This paper proposes a novel type of ribbon-to-single-fiber fanout connector applied to high-density high-count optical cables composed of fiber ribbons. The fanout connector provides individual access to fibers in the 10-fiber ribbon. Construction of the connector is made by assembling newly developed multifiber and single-fiber connectors: the former is a small plastic 10-fiber ribbon connector, and the latter is a push-on type single-fiber connector allowing easy push-pull reconnections. The fabricated fanout connector has shown an average insertion loss of 0.5 dB and a return loss of larger than 30 dB for the conventional graded-index multimode fibers. Mechanical and reconnectability test results have been entirely satisfactory for the practical use of the connector.