Fiber Optic PC Connectors: Single-channel vs. Multi-channel

Over the past 30 years, fiber optic technology has spanned its commitment constantly with the even more endeavors nowadays to meet the ever-increasing networking bandwidth for high-quality Internet applications. In these applications, fiber optic connectors, serving as mousetraps, are used to couple the source, receiver and other components to the fiber optic cable. Fiber optic connectors generally use either physical contact (PC) or expanded beam technology. This article mainly discusses PC connectors from single-channel and multi-channel aspects.

It’s necessary to figure out what PC connections are first.

What Are PC Connection?

A PC connection is accomplished by terminating the optical fiber into a precise ceramic ferrule. The tip of the ceramic ferrule is polished in a precise manner to ensure that light enters and exits at a known trajectory with little scattering or optical loss. In achieving PC connection, there are two requirements for a cleaved fiber endface for PC connection. One is that the fiber endface inclination is less than 0.6°, and the other is that there is no mist on the endface.

PC Connector Types

There are countless single-channel and multi-channel fiber optic PC connector types available for telecommunication and data-communication industries.

Single-channel Connectors

PC connectors are characteristic of directly mating and polishing fibers by utilizing tight tolerance ferrules and alignment sleeves and/or mating pins. This ceramic-ferruled technology permits reliable optical performance, with several designs becoming widely used as industry standards. Typically, these connectors are single fiber solutions with plastic shells. FC and ST connectors are becoming less popular but are still used in instrumentation. LC and SC connectors are commonly used in the telecommunication industry.

As a push-pull connector, LC connector, licensed by Lucent Technologies, provides a pull-proof design and small size perfect for high-density applications. It’s available in simplex or duplex versions, widely used in 10Gigabit, 40Gigabit and 100Gigabit applications. Like Cisco QSFP-40GE-LR4 transceiver, QSFP-40GE-LR4 listed on Fiberstore establishes 40Gigabit Ethernet (GbE) links with this duplex LC connector for 10km maximum link length over single-mode fiber (SMF).

SC connector, developed by Nippon Telegraph and Telephone (NTT), is recommended in the TIA/EIA-568-A Standard for structured cabling. It’s also available in simplex or duplex versions, typically used in Analog CATV (Cable Television) and other telecoms applications including point to point and passive optical networking.

Multi-channel Connectors

Multi-channel connectors house multiple fiber optic termini in a precision insertion. The termini can be configured as a pin/socket combination or genderless. MTP/MPO connectors belong to PC multi-channel connector.

The US CONEC MTP is a MPO compatible connector that exhibits quick and reliable connections for up to 12 fibers in a very small form factor. Just like LC connector, 40G links are likely to deploy this kind of MPO-12 connector for high performance. Take Cisco QSFP-40G-CSR4 for example, this QSFP-40G-CSR4 transceiver sets up 40G links in 850nm multi-mode fiber (MMF), with MPO-12 as its connector.

Optical Performance

Both single-channel and multi-channel PC connectors have optical performance characterized by return loss. The return loss of the connector is a measurement of how much light is reflected back at the connector interface. It’s affected by alignment, contamination and polishing. For example, if the mating faces of the two fibers are not parallel, some energy reflects back to the source. Additionally, contamination at the mating interface causes reflection and scattering of light. What’s more, a poor polish may create an end-gap separation or an end-angle.

Featuring by the tightest tolerance ceramic ferrules and alignment sleeves, coupled with the highest quality termination and polishing procedures, PC connections are able to deliver unrivaled optical performance.

Conclusion

Fiber optic connectors make quick fiber connection and efficient light transmission possible, gaining more and more popularity among their users. Fiberstore offers hundreds of fiber optic connectors, such as FC, D4, DIN, MU, the MTP/MPO ST, SC and LC, as well as their related optic modules (eg. QSFP-40GE-LR4 and QSFP-40G-CSR4 mentioned above). You can visit Fiberstore for more information about fiber optic connectors.

MPO/MTP Technology Overview

Along with the development of fiber technologies over the past a couple of years, tools for easier fiber connection have been invented—fiber optic connectors (or so-called “better mousetrap”). Given there are various fiber optic connectors (eg. ST, SC, LC, MPO/MTP) available for network designers to set up fiber connectivity in bandwidth-demanding applications, this article introduces MPO/MTP in details.

MPO/MTP technology with multi-fiber connectors ensures ideal conditions for establishing high-performance and high-speed data networks to handle bandwidth requirements. The term MTP is a registered trademark of US Conec used to describe their connector. The US Conec MTP product is fully compliant with the MPO standards. As such, the MTP connector is a MPO connector. The following passages will mention MPO only instead of MPO/MTP for simplicity. To let readers gain a better understanding of MPO technology, MPO components introduction goes first followed by the applications of MPO technology.

MPO Components

MPO (multi-position optical) connector contains up to 24 fibers in a single connection. It’s available in a male version (with pins) or a female version (without pins). The pins ensure that the fronts of the connectors are exactly aligned on contact and that the endfaces of the fibers are not offset. MPO connector components mainly contain two parts: adapter and cable.

MPO Adapters

There are two types of MPO adapters based on the placement of the key: key-up to key-down, and key-up to key-up. In the former type, the key is up on one side and down on the other. The two connectors are connected turned 180° in relation to each other. In the latter type, both keys are up. The two connectors are connected in the same position in relation to each other. Just like what’s shown in the figure below.

MPO Cables

MPO fiber cables are available in two primary types: MPO trunk cables and MPO harness cables.

MPO trunk cables are available in 12-144 counts. They serve as a backbone connecting the MPO modules to each other, intended for high-density applications.

MPO harness cables, also called MPO breakout cables or MPO fanout cables, are available in 8-144 counts. As terminated with MTP/MPO connectors on one end and standard LC/FC/SC/ST/MTRJ connectors (generally MTP to LC) on the other end, MPO harness cables provide a transition from multi-fiber cables to individual fibers or duplex connectors.

MPO Applications: 10 GbE to 40 GbE/100 GbE Migration

The remaining parts describe how MPO technology is utilized to permit successful migration from 10 GbE to 40/100 GbE.

It’s no doubt that converting or expanding existing infrastructure to accommodate higher bandwidth applications is more ideal and practical in data centers. In 10 GbE to 40 GbE/100 GbE migration, the most key point that should be kept in mind is the capacity expansion in which MPO modules are used to enable faster transmission. Many 40G QSFP transceiver modules utilize MPO technology for 40G links, among which the Cisco QSFP is the most widely-used module. Take Cisco for example, QSFP-40G-SR4 realizes 40G links over 850nm multi-mode fiber (MMF) with MPO-12 as its connector type.

In 40G to 100G migration, there requires the use of 24-fiber MPO cables. The existing 12-fiber connection can either be expanded with the addition of a second 12-fiber connection or can be replaced with the installation of a 24 fiber connection.

Conclusion

With these MPO components and technology applications, it’s easier for network designers to select the right MPO types to meet the bandwidth requirements. As a professional fiber optical product manufacturer and supplier, Fiberstore supplies various MPO modules and cables, including QSFP-40G-SR4 (one of Cisco QSFP products) mentioned above. You can visit Fiberstore for more information about MPO modules.