Multifiber Connector Research Articles

Evolution of optical fibre cabling components at CERN: Performance and technology trends analysis

Abstract CERN optical fibre infrastructure has been growing constantly over the past decade due to ever increasing connectivity demands. The provisioning plan and fibre installation of this vast laboratory is performed by Fibre Optics and Cabling Section at Engineering Department. In this paper we analyze the procurement data for essential fibre cabling components during a five-year interval to extract the existing trends and anticipate future directions. The analysis predicts high contribution of LC connector and an increasing usage of multi-fibre connectors. It is foreseen that single-mode fibres become the main fibre type for mid and long-range installations while air blowing would be the major installation technique. Performance assessment of various connectors shows that the expanded beam ferrule is favored for emerging on-board optical interconnections thanks to its scalable density and stable return-loss.

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.

MPO-type single-mode multi-fiber connector: Low-loss and high-return-loss intermateability of APC-MPO connectors

The electrical communication laboratory of NTT started the research of MT (Mechanically Transferable) connector in early 1980s. The initial goal was to realize a multi-fiber connector which can repeat low loss, stable, reliable and low-cost connections of subscriber optical fiber cable networks for more than 20 years period in the field. We review the multi-fiber alignment design with two guide pins, and following several technical improvements toward the final MT connector used in the commercial telecommunication networks. And then, we review development histories to reach to the low-loss, high-return-loss and reliable APC-MPO (Angled Physical Contact Multi-fiber Push On) connectors introduced in NTT COs and in Verizon’s FTTH (Fiber To The Home) networks. In the latter half, we propose the low-loss intermateability design for connectors made by different suppliers in order to enable mass introductions into large scale systems. In addition we also describe an accurate connector loss presumption method for different lots’ ferrules based on the MT ferrule dimension data before assembling the connectors. We believe with a wide intermateability of APC-MPO connector will increase its use in the fields. The APC-MPO connector manufactured based on the proposed design had low insertion losses of less than 0.25 dB at the same level of simplex connectors and the higher level of return losses higher than 65 dB.

Synchronous Parallel Optical I/O on CMOS: A Case Study of the Uniformity Issue

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Short-range parallel optical interconnect between integrated circuits can alleviate bandwidth, power, and packaging density issues that are associated with low-latency high-bandwidth input–output over electrical interconnect. In this paper, we evaluate the option of using true source-synchronous signaling over optical interconnect with a large number of channels, reducing the substantial per-channel clock synchronization circuitry to one instance. We also look into dc-unbalanced signaling to remove the need for data coding. Uniformity across channels is key to the feasibility of such an approach. An actual 64-channel parallel optical interconnect setup at 1.25 Gb/s/channel is examined, and models for the performance and uniformity of the different constituent parts of the interconnect are drawn up. Major attention is given to the statistical modeling of the coupling efficiency between a vertical cavity surface emitting laser array and a multifiber connector. Although derived in the context of a uniformity study, the stochastic models and the modeling approach are valuable in their own right. In our case study, the usage of a common logic threshold across all channels, which is required for dc-unbalanced signaling, appears infeasible after all models are combined. Efficient true source-synchronous signaling turns out to be within reach in carefully designed systems. </para>

Fabrication of a V-groove on the optical fiber connector using a miniaturized machine tool

As optical communication is being substituted for telecommunication, the demand of a large variety of fiber optic components is increasing. V-groove substrates, one of the module components, are used to connect optical fibers to optical planar circuits and to arrange fibers. Their applications are multi-channel optical connectors and optical wave-guide fiber coupling, etc. Because these substrates are a critical part of the splitter in a multiplexer and a multi-fiber connector, precise and reliable fabrication process is required. For precisely aligning core pitch between fibers, machined core pitch tolerance should be within submicrons. In general, these are produced by state-of-the-art micro-fabrication. However, most of the process equipment is very expensive. Also, it is difficult to change the process line for custom designs to meet specific requirements using various materials. For various design specifications such as different values of the V angle and for low-priced products, the fabrication method should be flexible and low cost. To achieve this goal, a miniaturized machine tool with high accuracy positioning was developed. It is shown in this present work, that this cutting process can be efficiently used to produce V-groove subtracts.

Development of a New Processing Method for Fiber Protrusion of Multi-fiber Connector.

A novel ultrasonic vibration polishing method was developed by introducing an assistant ferrule between the multi fiber connector and the ultrasonic vibrator, which enabled the ferrule endface to be processed exclusively without contact with fiber endface. By this method, the desired fiber protrusions of all the fibers in multi fiber connector were obtained efficiently in a short time so that good optical characteristics were achieved. Insertion loss difference of single mode 12 fiber connector with and without index-matching material was less than 0.04dB, and optical characteristics of 12 fiber connector without index matching material remained stable during the reconnections of 500 cycles. Good and stable physical contact (PC) connection was achieved. Compared with the conventional method, this novel method raises the processing efficiency greatly.

Single-mode multifiber connector using an injection molded MT type ferrule and a quick assembly technique

In this paper, we describe the design and performance of a newly developed single-mode multifiber connector which employs an injection molded mechanically transferable (MT) type ferrule and a quick assembly technique. The connector is designed to be compatible with the MT connector. The ferrule is made using injection molded thermoplastic resin. This makes the ferrule production process easier, and also contributes to cost effectiveness. The ferrule can be assembled without polishing or heating by fixing cleaved fibers with a quick hardening adhesive. The ferrule assembly time is only 3 minutes. The fabricated 8-fiber ribbon connector exhibits a low insertion loss of 0.21 dB and a return loss of >45 dB with index-matching.

Injection molded plastic multifiber connector realizing physical contact with fiber elasticity

We have proposed and demonstrated a fiber physical contact connector. This connector aligns multiple bare fibers in microholes individually and realizes physical contact by using the buckling force of the fibers themselves. The prototype is injection molded plastic and has a size of 7/spl times/24/spl times/3 mm for 8 fibers at a 0.25-mm pitch. The average insertion and return losses for single-mode fibers are under 0.2 dB and over 60 dB. These losses are stable in environmental tests.

Design and performance of a multifiber backpanel type connector

A compact multifiber backpanel type connector has been constructed by applying backpanel housings to multifiber push-on (MPO) type plugs. Fabricated backpanel type connectors for 8-fiber ribbons exhibit a low insertion loss of 0.2 dB and a high return loss of 60 dB.

Design and performance of an angled physical contact type multifiber connector

An angled, physical contact type multifiber connector is developed on the basis of a structural design which enables direct fiber endface contact between multifiber arrays. The direct contact is achieved by utilizing the elastic nature of a ferrule material under compressive force. The fabricated connector provides a low insertion loss of 0.2 dB and a high return loss of 58.8 dB without index-matching. This connector is used in the successful development of push-on type and backpanel type 16-fiber connectors with a low insertion loss of 0.25 dB and a high return loss of 58.0 dB for future subscriber networks.

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.

A fiber optic connector designed for military optical backplanes

A fiber optic connector designed to meet military stress requirements has been demonstrated. This reliable optical card-edge (ROC) connector is a multifiber backplane connector (four fibers, blind mate). The connector uses a unique expanded beam coupling design and micromachined silicon optical subassemblies to provide optimum coupling under high levels of shock and vibration. An additional feature of the ROC connector is its ability to self-seal or shield the optical fiber ends when unmated, protecting the fibers and internal mechanisms from environmental contamination and abusive handling. The design features of the ROC connector are discussed with respect to military stress requirements, and the prototype test results are presented. >

Design and performance of optical multifiber connector transfer splicing mechanism

The optical fiber cable transfer splicing mechanism by which existing fibers are transferred to new ones are considered and their dynamic characteristics are analyzed theoretically and verified experimentally. This paper describes the mechanical model of the horizontal and vertical movements of the ferrule in the transfer action and investigates its vibration characteristics. The vibration settling time is calculated and structural designs in realizing short-time transfers are described. It is shown that the previous movements of the guide pin inside the existing ferrule are effective in reducing the transfer time. The rapid transfer time of about 20 ms is shown to be achievable. Finally, using the manufactured transfer splicing mechanism, realization of 18 to 22 ms transfer time is verified experimentally. As to the reliability, it is indicated that the average splicing loss of 1500 splicing experiments is only 0.34 dB which shows satisfactorily good results.

A high-performance single-mode multifiber connector using oblique and direct endface contact between multiple fibers arranged in a plastic ferrule

A novel type of high-performance single-mode multifiber connector was developed using oblique and direct endface contact. This was obtained by butting a pair of obliquely polished plastic ferrules with a slight fiber protrusion. The fabricated connector offers a low insertion loss of 0.16 dB and a high return loss of 59 dB for single-mode four-fiber ribbons without index-matching. It enables easy reconnection and high performance for fiber ribbon cable joints. >

Subscriber single-mode optical fiber ribbon cable technologies suitable for midspan access

The loop network configuration and high-fiber-count, single-mode optical fiber ribbon cable and jointing technologies which enable a quick response to service demand and offer high reliability in the subscriber network are described. Fiber parameters were chosen for 1.3/1.55- mu m wavelength division multiplexing (WDM) transmission, and a 1000-fiber cable composed of 8-fiber ribbons was developed. A mass-fusion splicing technique and a multifiber connector were developed for the fiber ribbon. These techniques were evaluated by constructing an experimental line. It was found that they are highly suitable for midspan access, which is indispensable for the high-fiber-count loop network. >

Present Status of Mechanical Connectors for Optical Fiber

Trunk transmission network systems connecting exchange offices were the first transmission systems using fiber cables. Subscriber network systems connecting the exchange office with each subscriber including local area networks or CATV network systems are under development at present. Two main techniques are newly required to be developed for making fiber mechanical connectors for fiber subscriber network system realization. The first is to realize a new with a high return loss and a low connecting loss. The second is to cut the joining cost of fibers. The newly developed optical contact connector realized a high return loss of more than 25 dB and a low connecting loss of 0.15 dB average value. A newly developed connector which can connect many fibers at the same time can save time and space for joining fiber cables, and also a molding can save the cost of the The performance of all these connectors is the same as that of the optical contact connector. This paper describes the present status of the technique to obtain a high return loss connector, a multifiber connector, and a plastic molded for the subscriber network system.

Low-loss plastic molded optical multifiber connector for ribbon-to-single fiber fan-out

This paper describes a newly developed low-loss demountable multifiber connector for ribbon-to-single optical fiber fan-out. The connector plugs contain special gathering parts that make a high-density arrangement for monocoated optical fibers. Using a multi-V-grooved mold, the optical fibers are accurately positioned and then a plastic formation process is adopted to form the plug. Plugs are precisely aligned by using two pins. An average connecting loss of 0.07 dB has been achieved in the stationary mode distribution with index matching. The change in connecting loss did not exceed ± 0.03 dB when the connector was subjected to heat cycles in a temperature range of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-30-+60\deg</tex> C.

Optical fibre connectors using a fused and drawn multi-glass-rod arrangement

New demountable single-fibre and multifibre connectors have been constructed whose plugs include a precision multi-glass-rod arrangement, made by drawing, for locating the fibres and aligning pairs of plugs. The single-fibre and 6-fibre connectors exhibit an average insertion loss of 0.2 dB with index matching and an average off-axis of 3.5 μm. The connectors are potentially cost-effective and reliable.

Low-loss multifibre connectors with plug-guide-grooved silicon

Low-loss interchangable multifibre connectors have been developed using plugs consisting of large guiding grooved and fibre-fixing V-grooved silicon chips. Guiding grooves etched on silicon chips accomplish extremely small average fibre offset less than 2 μm. A 6-fibre connector plug pair selected from the same wafer exhibits 0.14 dB average connection loss. Connector plugs from different wafers exhibit 0.17 dB and 0.24 dB average connection losses.

Moulded multifibre connectors using rectangular multirod arrangement

Moulded demountable compact multifibre connectors have been constructed which have a rectangular arrangement of precision rods within the plug mouldings to locate the fibres in its interstices and to align pairs of plugs. The samples of 10-fibre connector tested so far have exhibited average insertion loss of 0.37 dB for step-index fibre 60 μm in core diameter. Connectors for an arbitrary number of fibres can be made from the same mould and parts by using this method.