Physical Contact Connection Research Articles

Reflowable optical connector with glass-ceramic ferrule for advanced pluggable transceiver packaging

Abstract We describe a new physical-contact optical fiber connector/receptacle that can withstand a solder-reflow process with a maximum temperature of 260 °C for advanced pluggable transceiver packaging such as the co-packaging of photonic and electronic chips using the reflow process. We experimentally clarify the problems that occur in the conventional simplex optical connector through the reflow process while discussing the glass-transition behavior of the adhesive used in the connector. We then present an improved receptacle structure with glass-based ferrules whose coefficients of thermal expansion are closer to that of the fiber compared to the conventional zirconia ferrule. We demonstrate through testing that our proposed receptacle results in a dramatic decrease of permanent fiber withdrawals after the reflow process. The proposed connector, which is composed of a glass-ceramic ferrule, a polyimide tube, and a mechanical clip, achieved physical-contact connection and maintained satisfactory connection and return losses of below 0.3 dB and over 45 dB, respectively, even after six reflow processes. We examined the withdrawal behaviors for both the zirconia and the glass-ceramic ferrules during reflow based on the online measurement of connection and return losses, and observed the multiple reflections caused by the change in the air-gap width between the mated connectors. We also confirmed that the developed simplex optical connectors based on the glass-ceramic ferrule yielded sufficient environmental durability even after multiple reflow processes.

Analysis of nano-creep deformation of epoxy adhesive in optical fiber connector for long-term reliability prediction

Abstract We describe a comprehensive analysis of the nano-creep deformation of an epoxy adhesive used in physical-contact optical fiber connectors. To design a highly reliable multicore fiber connector and predict the long-term reliability of commercially installed optical connectors, we focus on the change in fiber withdrawal, which is a key parameter for achieving physical-contact connection. We also propose an adhesive creep model that includes long-term time dependence by detailing through a finite element analysis the parameters that influence the fiber withdrawal, such as shear stress with connection, thermal stress, residual stress, swelling, and cure shrinkage. The measurement results for fiber withdrawal under several environmental conditions provided in this paper support the behaviors considered in our proposed model. From our obtained short-term results and rheological approach, we predict the nano-creep deformation observed in the connector over the long term by applying the time-temperature superposition principle, and discuss the correspondence with exposure test results. Our verified mechanism and estimated values of creep deformation prove the high reliability of the optical connectors and also provide guidelines for determining the need to update installed connectors and for designing future connection devices such as physical-contact multicore fiber connectors.

Two-photon direct laser writing of beam expansion tapers on single-mode optical fibers

Small misalignments between two standard telecom single-mode fibers in a physical contact connection can lead to large optical losses. It is known that by expanding the mode field diameter of the fiber, the misalignment tolerances can be relaxed. One of the approaches to obtain this beam expansion is to use tapers. We propose an air-clad taper structure to transmit the fundamental mode of a single-mode fiber adiabatically to a 3 times larger mode field area in physical contact expanded beam connectors. This results in a 241.4 μm long linear taper. The taper itself is fabricated on top of a cleaved fiber facet by means of the two-photon polymerization direct laser writing technique. Experimental results for lateral misalignment show excellent agreement with simulated values and give an increase in lateral misalignment tolerance of 1 μm (−1 dB) and 1.8 μm (−3 dB). Total insertion losses down to 0.76 dB are measured, showing the trade-off between achievable insertion loss and misalignment tolerance relaxation. Finally, we show that the use of additive manufacturing techniques in fiber beam expansion applications make it possible to fabricate taper structures with full 3D design freedom and to upscale the process to multi-fiber components.

Low-Loss and Low-Mode-Dependent-Loss Fan-In/Fan-Out Device for 6-Mode 19-Core Fiber

This paper describes a low-loss fiber-bundle-type fan-in/fan-out (FI/FO) device for 6-mode 19-core fiber, which exhibits a low mode-dependent loss (MDL) with a physical-contact connection for all the cores. We reveal that reducing the offset at the connection of few-mode fibers (FMFs) at butt coupling does not necessarily result in a minimum MDL, and the FMFs should be aligned so as to minimize the MDL, by experimentally investigating the MDL as a function of the lateral offset at butt coupling. We develop a precise rotational alignment mechanism to accurately adjust the core position without any complex alignment equipment, and we introduce a hexagonal microhole into a ferrule to accurately arrange the fibers. With these technologies, we successfully suppress the mode-dependent loss of the FI/FO device. The device provides a low MDL variation of less than 2 dB for all the cores with good optical properties such as a low excess loss, low core-to-core crosstalk, and a high return loss. The fabricated FI/FO device also achieved the highest reported spatial multiplicity connection of more than 100 with a small footprint as well as a low connection loss. Other optical properties that we obtained such as the modal crosstalk are also described.

Multi-core Fiber Connector Technology for Low-loss Physical-contact Connection

Multi-core Fiber Connector Technology for Low-loss Physical-contact Connection

MPO Type 8-Multicore Fiber Connector With Physical Contact Connection

We developed a MPO type 8-multicore fiber (MCF) connector using single mode 7-core MCF and realized physical contact (PC) with return loss more than 40 dB and low connection loss less than 0.85 dB in all 56 cores. To simplify the rotational alignment process for each MCF, we developed the rotational alignment method using alignment member and realized rotational alignment accuracy within ±1°. To reduce necessary pressing force for PC connection of all cores in all MCFs, we utilized compressive strain of MCF cladding for the absorption of height difference among MCFs and polishing for bare MCF to reduce necessary pressing force for a pair of MCFs. Fabricated 8-MCF connector demonstrated all cores PC with pressing force of 18 N.

Multicore Fiber Connector with Physical-Contact Connection

Multicore Fiber Connector with Physical-Contact Connection

Multiple multicore fibre connector with physical‐contact connection

A new multiple multicore fibre (MCF) connector is presented that employs the compressive deformation of the fibre in a multiple ferrule. This connector enables a physical-contact connection for all the fibre cores including the outer ones with a small compression force even if the connector end has manufacturing errors. The connector has been designed and fabricated for a 7-core single-mode MCF connector taking account of the relationship between the connector end structure and compression force, and it achieves physical contact connection with a connection loss below 0.7 dB and a return loss exceeding 54 dB.

Physical‐contact‐type fan‐out device for multicore fibre

Demonstrated is a fan-out device using small diameter fibres for 7-core singlemode multicore fibre, which realises a compact size with ferrules and a split sleeve, and also achieves physical contact connection with an average connection loss of 0.17 dB and a return loss exceeding 49 dB.

Novel field installable optical fiber splice and connector for optical access networks

We have developed two types of field installable connection techniques. One is mechanical splicing, which is used to connect coated optical fibers without the need for stripping or cleaning procedures. The other is a field assembly connection technique, which employs a new type of field installable connector that makes it possible to realize a physical contact connection with chamfer grinding. Mechanical splicing is achieved by precisely aligning and directly connecting coated fibers with a capillary. The assembled splice is installed with 1.3-μm single-mode fibers that have an 80-μm cladding and a 125-μm coating and they exhibit good optical performance with a low average insertion loss of 0.2dB. Connection is achieved with our developed field installable connector by using a chamfered fiber endface and the compression force of the buckled fiber. The assembled connectors achieve physical contact with the chamfered fiber endface, which provides good optical performance with a low insertion loss of 0.11dB.

Physical Contact Connection Between SC Connector and Raw Cleaved SM-Fiber End

We achieve a physical contact (PC) connection by using simple butt jointing between an SC connector and a raw cleaved single-mode (SM) fiber end without index matching material. We show that there are two requirements for a cleaved fiber endface for PC connection. One is that the fiber endface inclination is less than 0.6 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , and the other is that there is no mist on the endface. The cleaving condition is also discussed to allow us to consistently obtain an appropriate endface. A crack depth of less than 5 μm and a bending radius of 100 mm before breaking are the optimum values in the conventional fiber cleaving process. The average insertion and return losses are 0.14 and 51.1 dB, respectively, and these values are similar to those for a conventional SC connector.

Focus on lasers and imaging

Focus on lasers and imaging

Design and Performance of Field Installable Optical Connector Realizing Physical Contact Connection without Fiber Endface Polishing

We propose and demonstrate a new type of field installable optical connector that enables us to realize physical contact connection without polishing the fiber endface by using a sharpened fiber endface and the compression force of buckled fiber. We confirmed that all the assembled connectors achieved physical contact connection without the fiber endface being polished, and provided good optical performance with a low insertion loss of 0.08 dB and a high return loss of over 49 dB.

10-year reliability test results for SC connector installed on outside plant

Optical connectors are used both indoors and outdoors. To confirm the durability of optical connectors employing PC connection in actual outdoor environments, since 1997 we have been performing a reliability test on an SC connector installed in a high temperature and high humidity location. We confirmed that SC connectors with optimized ferrule end dimensions, which are designed to provide physical contact connection with long-term reliability, have maintained good levels of optical performance in an actual outdoor environment for 10 years.

Optical Characteristics and Reliability of 16-Fiber Fiber Physical Contact Connector with Zirconia Ceramic Micro-Hole Array

Optical connectors for printed circuit board interfaces are required for the implementation of reliable high-density multi-fiber connection. We developed a 16-fiber fiber physical contact (FPC) connector with an MU connector coupling mechanism and a compact shutter to meet this requirement. In the FPC connector, two arrays of fibers are aligned in micro-holes without ferrules. A micro-hole array is a key component as regards the optical characteristics of the FPC connector. We developed a 16-ch micro-hole array composed of injection molded zirconia ceramics. The 16-liber FPC connectors with a zirconia ceramic micro-hole array had an insertion loss of less than 0.3 dB with an average value of 0.07 dB and a return loss of over 45 dB. The optical characteristics remained stable in environmental and mechanical tests.

PLC connector with PLC-fiber physical contact for multichannel receptacle PLC modules for optical circuit board integration

We describe a novel waveguide-fiber connector, namely, the planar lightwave circuit (PLC) connector, designed to realize a receptacle interface in PLC-based optical modules for economical optical circuit board integration. This connector can provide stable high-density multiple connection between a PLC and single-mode fibers. Moreover, this connector is inexpensive to produce because it utilizes physical contact (PC) connection between a PLC and fibers by employing the elastic force generated by the fibers themselves rather than by a ferrule and spring. We fabricated a duplex PLC connector and a multiple PLC connector for an optical transceiver module and multichannel optical modules, respectively, and successfully obtained low average connection losses of 0.2 and 0.33 dB, and high average return losses of 43 and 43 dB, respectively. In addition, we confirmed that the connectors had sufficient environmental durability. We also realized 2- and 34-channel receptacle interfaces in the transceiver module and a thermooptic switch module by equipping the modules with the duplex connector and three of the multiple connectors.

Study of fiber management for optical board integration

AbstractWith a view to high‐density integration and high production integration of printed circuit boards for installation of optical devices (optical boards), FMOB (Fiber Management for Optical Board integration) is investigated. Fiber Physical Contact connectors to realize high‐density multi‐core fiber connection, PLC connectors to realize direct connection with PLC, and fiber wiring board are developed as element technologies. The earlier fiber integration process by fused connection is replaced with connector joining of fiber wiring components. FMOB is applied to an 8 × 16 delivery and coupling switch board for photonic transport systems. Practically sufficient optical performance, improvement of the integration density, and enhancement of work efficiency are confirmed, demonstrating the effectiveness of the FMOB. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 85(7): 37–47, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10023

High-power performance of single-mode fiber-optic connectors

We measured the continuous wave (CW) laser-induced damage threshold of single-mode fiber-optic connectors at 1550 nm. Clean standard physical contact and angled physical contact connectors did not show any evidence of damage for 10 min exposures of 1 W or 3 W. Defective connectors with scratched or undercut endfaces showed identical high-power tolerance as clean connectors without defects. Samples contaminated with carbon black-doped acrylate showed drastic optical failure signatures at approximately 50 mW. Contaminated connectors with expanded mode field diameters ranging from 20 to 62 /spl mu/m showed higher failure thresholds than standard connectors with 10-/spl mu/m spot sizes. We observed that the optical failure threshold power level (P/sub failure/) increased linearly with spot size for the highly contaminated connectors used in this study.

Study of surface mounting of PLC on optical fibre circuit board

The first surface mounting of a planar lightwave circuit (PLC) on an optical fibre circuit board is proposed and demonstrated. Both surface mounting and physical contact connection between a PLC type duplex 1/spl times/16 splitter and fibres were realised.

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.