White Papers

Spring Force Requirements for MPO Connectors

October 2020

Abstract: Stringent endface geometry requirements are necessary to achieve physical contact in fiber optic connections. Previous studies of MT ferrule endface geometry requirements have focused on single 12 fiber arrays. Standardized spring forces and endface geometries may become insufficient to maintain physical contact for higher fiber counts. This paper examines the critical parameters, including the spring force and ferrule geometry, needed to achieve physical contact for MT-16 based ferrules and to ensure optimal insertion loss and return loss performance for mated connector assemblies.
Results indicate that multimode flat and angled interfaces, with fiber counts of 16 or greater, can benefit from spring forces higher than 12 fiber ferrules. Single-mode angled interfaces, with 16 fibers in a single array, present additional core alignment challenges due to the y-directional shift that occurs when mating. For these connectors, 10N spring force may be sufficient. © 2020 IWCS International Cable & Connectivity Symposium. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.

Solder Reflow Capable Multifiber Ferrule for Co-Packaged Optics

September 2020

Abstract: Multifiber MT ferrules molded from a high temperature material exhibit significantly improved solder-reflow performance. CTE and Tg data is reported and compared to conventional multifiber ferrules. Dimensional measurements demonstrate that the ferrules are capable of surviving multiple reflow cycles. © 2020 US Conec, Ltd. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.

Bridging the Gap: Manufacturing Optical Transceivers in the Multibillion-Dollar Silicon Electronics Supply Chain

February 2020

Abstract: Juniper’s silicon photonics technology employs an entirely new approach to optics manufacturing that leverages design, wafer manufacturing, packaging and test infrastructure and methodologies from the microelectronics ecosystem, resulting in a fabless optical transceiver manufacturing flow cable of scaling, in both cost and performance, with the needs of the networking industry. Juniper’s fully integrated “Opto-ASIC” transceiver leverages densely packaged electronic and photonic die in a single, low-cost package that supports common module form factors as well as on-board and on-package optics applications. The ability to incorporate all optical components, including lasers, within a single, common silicon die is a key enabler of the approach, fundamentally changing and simplifying how an optical transceiver can be assembled and tested. We will review lessons learned and provide a preview of the road ahead. © 2020 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. Proc. SPIE 11286, Optical Interconnects XX, 112860H (28 February 2020); https://doi.org/10.1117/12.2550937. **Authored by Juniper featuring US Conec technology**

Detachable 1x8 Single Mode Optical Interface for DWDM Microring Silicon Photonic Transceivers

February 2020

Abstract: We are developing a 1x8 single mode (SM) optical interface to facilitate the adoption of dense wavelength division multiplexing (DWDM) silicon photonic (SiPh) optical interconnects in exascale computing systems. A common method for fiber attachment to SiPh transceivers is ‘pigtailing’- the permanent adhesive bonding of fiber/v-groove arrays to onchip grating couplers (GC). This approach precludes standard high throughput surface mounting and solder reflow assembly of the transceiver onto system printed circuit boards. Our approach replaces the fixed pigtail with a low profile, small form factor, detachable expanded beam optical connector which consists of four essential parts: a GC array, a surface mount glass microlens array chip, an injection molded solder reflowable optical socket, and an injection molded SM light turn ferrule. The optical socket and ferrule are supplied by US Conec Ltd. To design the GC, we developed an optical simulator that considers CMOS foundry constraints in the optimization process. On-wafer measurements of the GC coupling loss to SMF28 fiber at 1310nm is ~1.4dB with a 1dB bandwidth of ~22nm. This ensures a wide low loss spectral window for at least 16 DWDM channels. The geometry of the optical system is arranged so that only a simple spherical lens is required for efficient mode matching in the expanded beam space. The fiber to fiber insertion loss through the light turn ferrule, two microlenses and GCs, and a looped back SOI waveguide ranged from 4.1-6.3dB, with insertion loss repeatability of 0.2dB after multiple mating cycles. © 2020 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. Proc. SPIE 11286, Optical Interconnects XX; 112860A (2020); https://doi.org/10.1117/12.2544400.

Injection Molded Low-Thermal-Expansion Multi-fiber Ferrule

February 2020

Abstract: Hybrid injection-molded ferrules are presented which consist of a polymer body and an over-molded glass insert. The average coefficient of thermal expansion observed at the front face of the ferrules is 8 ppm/C from room temperature to 100 C. This design could be applicable for direct heterogeneous re-matable connections between fiber ribbons and photonic integrated circuits which exhibit low thermal expansion and operate at elevated temperatures. © 2020 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. Proc. SPIE 11286, Optical Interconnects XX; 112860T (2020); https://doi.org/10.1117/12.2545040.

CWDM MUX/DEMUX Passive Optical Interconnect

February 2020

Abstract: A novel concept for integrating the MUX/DEMUX functionality of coarse wavelength division multiplexing (CWDM) into passive fiber optic connectors via expanded beam ferrules is presented, including optical modeling and preliminary empirical results. © 2020 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.

Increasing Duplex Connector Density While Maintaining User Accessibility

September 2019

Abstract: As data consumption continues to increase, so does the relative bandwidth of data centers, central offices and head-ends. Reducing the overall optical hardware footprint in these highly controlled environments reduces real estate capital expenses, maintenance and speeds up installation. One method to achieve a reduced hardware footprint is by increasing connector density at the panel and transceiver by reducing the size of the connector and adapter. Until now, the smallest standardized single fiber connector is the LC connector, with a typical 1 rack unit capacity of 144 fibers. The LC connectors are commonly installed in pairs, called duplex LC, for transmit and receive communications. A new Very Small Form Factor (VSFF) connector, the MDC connector, was developed in an effort to achieve an appropriate balance of usability with minimal size while continuing to meet the carrier grade performance requirements of Telcordia GR-326. © 2019 US Conec, Ltd. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.

A Single-Mode Expanded Beam Separable Fiber Optic Interconnect for Silicon Photonics

March 2019

Abstract: An expanded beam optical interconnect is introduced that provides a separable connection between photonic integrated circuit and single-mode fiber. Insertion loss data are provided and stability through solder reflow is demonstrated. © 2019 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.

CWDM Transceiver for Mid-Board Optics

February 2017

Abstract: The need for additional IO bandwidth for data center device interconnection is well established. Optical interconnects can deliver required bandwidth along with energy and space efficiency at a cost that encourages adoption. To this end, we are developing an optical transceiver incorporating multimode VCSEL emitters in a coarse wavelength division multiplex (CWDM) system capable of transmission at 25Gbps per channel, 100Gbps/fiber, and a maximum aggregate bidirectional data rate of 1.2Tbps. Electrical connection to the transceiver can be made by solder reflow or LGA connector, and optical connection is made by means of a custom optical connector supporting CWDM transmission. © 2017 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. Proc. SPIE 10109, Optical Interconnects XVII, 101090B (20 February 2017); https://doi.org/10.1117/12.2250610

A Mechanical-Optical Interface for 25+ Gbps VCSEL/PD Fiber Coupling

January 2017

Abstract: As parallel optics data rates transition from 10 Gbps to 25 Gbps and beyond, VCSELs and photodiodes (PDs) are evolving to support the higher transmission rates. In order to maintain system performance as speeds increase and tolerances become tighter, an improved method is needed to efficiently couple VCSEL/PD array optical outputs to fiber optic networks. The mechanical-optical interface (MOI) is a monolithic component with an array of collimating lenses designed for efficient coupling between the on-board active components and a detachable fiber optic connector. © 2017 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

Performance Methodology and Characterization of a Multi-Fiber Expanded Beam Lensed Optical Interconnect

April 2016

Abstract: The demand for high performance, cost-effective optical interconnects is driving the need for novel connectors in the optical communication industry. A multi-fiber lensed ferrule has been introduced that addresses backplane and ganged application requirements through the use of molded, expanded beam optics. The new ferrule maintains the same footprint as traditional multi-fiber ferrules, but uses an array of lenses on the front face to expand and collimate up to sixty-four channels simultaneously. The monolithic ferrule uses a hermaphroditic post and hole mating system to eliminate the costs associated with traditional steel alignment pins. The final result is a collimated beam connector system that enables debris insensitive connections for standard multi-mode optical fiber. © 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

Multi Fiber Connector Technologies

March 2015

Abstract: This paper describes the advancement of high density optical interconnect components which is enabling high bandwidth, low cost, single-mode and multimode optical communication between IC’s for on-card, optical backplane and chassis to chassis applications. © 2015 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.

Development and Qualification of a Mechanical Optical Interface for Parallel Optics Links

February 2015

Abstract: As parallel optics applications continue to expand, there remains a need for an effective coupling interface between the board-level active components and the passive components of the network. While mid-board level photonic turn connectors are available, coupling interfaces are generally not available outside of proprietary solutions. Development of a general mechanical-optical coupling interface opens the door for broader parallel optics implementation. © 2015 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

Theoretical and Empirical Qualification of a Mechanical Optical Interface for Parallel Optics Links

February 2015

Abstract: As the implementation of parallel optics continues to evolve, development of a universal coupling interface between VCSEL/PD arrays and the corresponding photonic turn connector is necessary. A newly developed monolithic mechanical-optical interface efficiently couples optical transmit/receive arrays to the accompanying fiber optic connector. This paper describes the optical model behind the coupling interface and validates the model using empirical measurements. © 2015 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

Design and Performance of Expanded Beam, Multi-Fiber Connectors

January 2015

Abstract: A multi-fiber, molded, monolithic, expanded beam ferrule had been designed, manufactured and tested to confirm the viability of low cost, no-polish, debris insensitive ferrule for single mode applications. This interconnect technology is ideal for passive interconnects at the equipment, card-edge interface with embedded optic technology where cost, density, debris sensitivity and coupling force are of concern. Parts were manufactured to the specifications assumed in the optical simulations. Empirical data from randomly mated connector pairs was collected and confirmed to closely match the predicted results from the optical Monte Carlo simulation. © 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

New, Single-Mode, Multi-Fiber, Expanded Beam, Passive Optical Interconnect

March 2014

Abstract: This paper describes the design and performance of next generation, single-mode, multi-fiber, debris insensitive, expanded beam, interconnect components. This low cost, dense optical interconnect technology combined with recent advances next generation, high bandwidth, SM, silicon photonic based Tx/Rx devices is enabling unprecedented bandwidth densities for extended distances at reduced costs. A monolithic, multi-fiber ferule with integrated collimating lenses was designed with the same overall footprint as a traditional MT-type, multi-fiber rectangular ferrule. The new optical ferrule was designed with precision micro holes for alignment to the lens array allowing for future incorporation of multiple rows of fibers into a single ferrule unit. The monolithic, lensed based ferule design enables a low-cost, no-polish fiber termination methodology. The ferrule tested was manufactured with an array of 16 fibers in the footprint associated with traditional, 12 fiber, physical contact MT ferules via use of novel, molded in, end-face alignment features. Multiple optical models were built with ray tracing methodology to predict the insertion loss and return loss with varying refraction index, transmissivity and surface reflection properties of the ferrule. Empirical optical performance results closely match the optical modeling predictions. Insertion losses of <1.5dB were measured along with return loss values <=-30dB. Further analysis was done to characterize the robustness of the new interconnect with regard to debris insensitivity. Do to the nature of the expanded beam, free-space optical design, the impact of debris on the optical mating surface of the interconnect was significantly reduced when compared to traditional, physical contact single-mode interconnects © 2014 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. Proc. SPIE 8991, Optical Interconnects XIV, 89910J (8 March 2014); https://doi.org/10.1117/12.2043171

High Density, Low Cost, No-Polish Optical Ferrule

July 2013

Abstract: A monolithic, multi-fiber ferule with integrated collimating lenses with the same overall footprint as a traditional MT-type ferrule was tested for insertion loss and return loss, before and after durability testing without cleaning. © 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

Performance Methodologies of a Modular Miniature Detachable Photonic Turn Connector

February 2013

Abstract: Next generation parallel optical interconnects that incorporate monolithic collimating lens arrays require new procedures and guidelines for performance certification and visual inspection. This paper, after reviewing design specifications, will report performance methodologies for a modular miniature photonic turn connector that is used as an interface into VCSEL and photodiode arrays. A new insertion loss test procedure is introduced that can be used to screen connector performance without the need for vendor-specific optical engines. Data will be presented to show how induced defects affect the connector performance and thus establish inspection criteria. Finally, recommended cleaning procedures will be addressed. © 2013 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. Proc. SPIE 8630, Optoelectronic Interconnects XIII, 863003 (27 February 2013); https://doi.org/10.1117/12.2006419

Next Generation, High Density, Low Cost, Multimode Optical Backplane Interconnect

February 2012

Abstract: This paper describes the development, termination and performance of next generation optical backplane interconnect components. This low cost, dense optical interconnect technology combined with recent advances in 10G/lane and beyond, miniature imbedded Tx/Rx devices is driving bandwidth density to unprecedented levels. A monolithic, multi-fiber ferule with integrated collimating lenses was designed with the same overall footprint as a traditional MT-type, multi-fiber rectangular ferrule. The new optical ferrule was designed with precision micro holes for alignment to the lens array allowing for incorporation of multiple rows of fibers into single ferrule unit. The design supports up to four rows with as many as 16 fibers per row for a total potential lane count of up to 64 within in a single ferrule. A low cost termination is achieved by securing precision-cleaved fiber arrays into the rear of the ferrule with a quick-cure, index matched, UV light activated epoxy. The elimination of a polished fiber array greatly reduces the cost and complexity associated with physical contact based multi-fiber interconnects. With the same overall footprint as an MT ferrule, the new, lens-based ferrule can be used in conjunction with MPO and other MT based connectors. However, by eliminating the need for physical contact via the use of collimated light beams, the connection force per ferrule required is greatly reduced, paving the way for high ferrule counts and mass insertion of dense optical backplanes. Mated pairs of the new ferrule were tested for insertion loss with the substitution method and all channels were <1dB. © 2012 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. Proc. SPIE 8267, Optoelectronic Interconnects XII, 82670O (2 February 2012); https://doi.org/10.1117/12.909688

Miniature Detachable Photonic Turn Connector for Optical Module Interface

June 2011

Abstract: Miniature embedded parallel optic modules are newly available and currently being designed into system equipment solutions to address the expanding requirement for very dense I/O bandwidth. These embedded miniature parallel optic modules greatly improve component densities by significantly reducing the board level footprint requirements of traditional parallel optic modules such as SNAP12, POP4, QSFP and the recent CXP specification. Implementation of these small form factor modules facilitates the ability to pack more processing power onto the physical board, thereby conserving valuable space and power in data centers. These mid-board mounted miniature modules enable the use of high density optical connectors, such as 24 and 48-fiber MPO type connectors at the card edge. These high density optical connectors significantly improve the interconnection density and operational function at the card edge over traditional front panel mounted parallel optics. Fiber optic jumper cables are used to provide the optical interface between the miniature embedded parallel optic modules and the high density optical connector at the card edge. Application issues to this enhanced embedded parallel optic system exist when the optical interface into the module does not equally facilitate the system value achieved by the miniature module and high density card edge connector. To complement the benefits offered by implementation of a miniature optical module, an equally innovative and economical module connector interface is required. This module connector must enhance the functionality of providing the optical jumper interface between the module and high density connector at the card edge. The design solution presented herein is a low cost, low profile connector system that provides a reliable, consistent, and repeatable mating interface to the miniature optical module. It achieves the design and performance requirements needed to effectively implement these new high density parallel optic systems. © 2011 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

Multi-Fiber, MT Ferrule Endface Fiber Tip Displacement Model for Physical Contact Interconnects

2007

Abstract: This paper describes a simplified model linking MT ferrule and connector attributes to positive contact performance. Validation with FEA, experimental apparatus and empirical results are described, along with topics for future study. © 2007 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.