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.


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.

LC Connector Family

The LC connector developed by Lucent Technologies and shown in Fig.3.10 is a more evolutionary approach to achieving the goals of a SFF connector. The LC connector utilizes the traditional components of a SC duplex connector having independent ceramic ferrules and housings, with the overall size scaled down by one-half. The LC family of connectors includes a stand-alone simplex design; a “behind the wall” (BTW) connector and the duplex connector available in both single-mode and multimode tolerances are all designed using the RJ-style latch.

The outward appearance and physical size of the LC connector varies slightly depending on the application and vendor preference. Although all the connectors in the LC family have similar latch styles modeled after the copper RJ latch, the simplex version of the connector has a slightly longer body than either the duplex or BTW version, and the latch has an additional latch actuator arm that is designed to assist in plugging as well to prevent snagging in the field. The BTW connector is the smallest of the LC family and is designed as a field-or board-mounatable connector using 900-um buffered fiber and in some cases has slightly extended latch for extraction purposes. The duplex version of this connector has modified body to accept the duplexing clip that joins the two connector bodies toghther and actuates the two latches as one. Finally, even the duplex clip itself has variations depending on the vendor. In some cases the duplex clip us a solid one-piece design and must be placed on the cable prior to connectorization, while other design and must be placed on the cable prior to connectorization, while other designs have slots built into each side to allow the clip to be installed after connectorzation. In coclusion, all LC connectors are not created equal, and depending on style and manufacturer’s preference, there may be attributes that make one connector more suitable for a specific application then another.

The LC duplex connector incorporates two round ceramic ferrules with outer diameters of 1.25mm and a duplex pitch of 6.25mm. These ferrules are aligned through the traditional couplers and bores using precision ceramic split or solid sleeves. In an attempt to improve the optical performance to better than 0.10 db at these interfaces, most of the ferrule and backbane assemblies are designed to allow the cable manufacturer to tune them. Tuning of the LC connector simply consists of roating the ferrule to one of four available positions dictated by the backbone design. The concept is basically to align the concentricity offset of each ferrule to a single quadrant at 12.00; in effect, if all the cores are slightly offset in the same direction, the probalility of a core-to-core alignment is increased and optimum performance can be achieved. Although this concept has its merits, it is yet another costly step in the manufacturing process, and in the case where a tuned connector is mated with an untuned connector, the increase in performance may not be realized.

Typically, the LC duplex connectors are terminated onto a new reduced-size zipcord referred to as mini-zip. However, as the product matures and the applications expand, it may be found on a number of different cordages. The mini-zip cord is one of the smallest in the industry with an outer diameter of 1.6mm compared with the standard zipcord for an SC style product of 3.0 mm. Although this cable has passed industry standard testing, the cable manufacturers have raised some issues concering the ability of the 900-um fibers to move freely inside a 1.6-mm jacket and others involving the overall crimped pull strengths. For these reasons, some end users and calbe manufactures are opting for a larger 2.0-mm, 2.4-mm, or even the standard 3.0-mm zipcord. In application wher the fiber is either protected within a wall outlet or cabinet, the BTW connector is used and terminated directly onto the 900-um buffers with no jacket protection.

The factory termination of the LC cable assemblies is very similar to order ceramic-based ferrules using the standard pot and polish processes with a few minor differences. The one-piece design of the connector minimizes production handling and helps to increase process yields when compared with other SFF and standard connector types. Because of the smaller diameter ferrule, the polishing times for an LC ferrule may be slightly lower than the standard 2.5-mm connectors, but the real production advantage is realized in teh increase number of connectors that can be polished at one time in a mass polisher. For the reasons mentioned above and because the process is familiar to most manufacturers, the LC connector may be considered one of the eaisest SFF connectors to factory terminate.

Field termination of the LC connector has typically been accomplished through the standard pot and polish techiques using the BTW connector. However, a pre-polished, crimp and cleave connector is also available. The LCQuick Light field-mountable BTW style connector made by Lucent Technologies is a one-piece design with a factory polished ferrule and an internal cleaved fiber stub. Unlike other pre-polished SFF connectors previously discussed, the LCQuick light secures the inserted field cleaved fiber to a factory polished stub by crimping or collapsing the metallic entry tube onto the buffered portion. This is accomplished by using a special crimp tool that is designed not to damage the fibers. However, light is designed specifically for use in protected environments such as cabinets and wall outlets and has no provision for outer jacket or Kevlar protection.

LC connections allow higher density applications based on its smaller diameter. The LC connection, commonly referred to as Lucent Connection, Little Connector or Local Connector, is commonly used today for uplink modules and other devices. This connector is a “snap” type, has a ferrule diameter of 1.25mm and defined by IEC 61754-20. We offer LC fiber cables and lc lc cable, including single mode 9/125 and multimode 50/125, multimode 62.5/125, LC-LC, LC-SC, LC-ST, LC-MU, LC-MTRJ, LC-MPO, LC-MTP, LC-FC, OM1, OM2, OM3. Other types also available for custom design. Excellent quality and fast delivery.

The LC fiber patch cable cable is with a small form factor (SFF) connector and is ideal for high density applications. The LC fiber patch connector has a zirconia ceramic ferrule measuring 1.25mm O.D. with either a PC or APC end face, and provides optimum insertion and return loss. The LC fiber patch cable connector is used on small diameter mini-cordage (1.6mm/2.0mm) as well as 3.0mm cable. LC fiber cable connectors are available in cable assembled or one piece connectors. The LC fiber optic assemblies family is Telcordia, ANSI/EIA/TIA and IEC compliant.