Connectivity Solutions for Duplex and Parallel Optics

In optical communication, duplex and parallel optical links are two of the most commonly deployed cabling structures. This post will discuss some specific connectivity solutions using 2-fiber duplex and 8-fiber/20-fiber parallel fiber optic modules.

Duplex and Parallel Optical Links

A duplex link is accomplished by using two fibers. The most commonly used connector is the duplex LC. The TIA standard defines two types of duplex fiber patch cables terminated with duplex LC connector to complete an end-to-end fiber duplex connection: A-to-A patch cable (a cross version) and A-to-B patch cable (a straight version). In this article the LC to LC duplex cables we use are all A-to-B patch cables. It means the optical signal will be transmitted on B connector and received on A connector.

two types of duplex-patch-cable

Figure 1: two types of fiber patch cables

A parallel link is accomplished by combining two or more channels. Parallel optical links can be achieved by using eight fibers (4 fibers for Tx and 4 fibers for Rx), twenty fibers (10 fibers for Tx and 10 fibers for Rx) or twenty-four fibers (12 fibers for Tx and 12 fibers for Rx). To accomplish an 8-fiber optical link, the standard cabling is a 12-fiber trunk with an MTP connector (12-fiber connector). It follows the Type B polarity scheme. The connector type and the alignment of the fibers is shown in figure 2.

8-fiber parllel system

Figure 2: parallel fiber (8-fiber) optic transmission

To accomplish a 20-fiber parallel optical link, a parallel 24-fiber MTP connector is used. Its fiber alignment and connector type is shown in figure 3.

20-fiber parallel system

Figure 3: parallel fiber (20-fiber) optic transmission
Duplex Fiber Optic Transmission Links (2-fiber to 2-fiber)

We will discuss the items required to connect two duplex transceivers in this part. These 2-fiber duplex protocols include but not limited to: 10GBASE-SR, 10GBASE-LR, 10GBASE-ER, 40GBASE-BiDi, 40GBASE-LR4, 40GBASE-LRL4, 40GBASE-UNIV, 40GBASE-FR, 100GBASE-LR4, 100GBASE-ER4, 100GBASE-CWDM4, 100GBASE-BiDi, 1GFC, 2GFC, 4GFC, 8GFC, 16GFC, 32GFC.

Duplex Direct Connectivity

When directly connecting two duplex SFP+ transceivers, an A-to-B type patch cable is required. This type of direct connectivity is suggested only to be used within a given row of racks/cabinets. Figure 4 shows two SFP+s connected by one LC to LC duplex patch cable.

2-fiber to 2-fiber direct connectivity Figure 4: 2-fiber to 2-fiber direct connectivity

Duplex Interconnect

The following figure is an interconnect for two duplex transceivers. An 8-fiber MTP trunk cable is deployed with 8-fiber MTP-LC breakout modules connected to the end of the trunk. It should be noted that the polarity has to be maintained during the transmission. And pinned connectors should be deployed with unpinned devices. Structured cabling allows for easier moves, adds, and changes (MACs). Figure 5 illustrates this solution.

2-fiber to 2-fiber interconnect (1)

Figure 5: 2-fiber to 2-fiber interconnect (1)

Item Description
1 LC to LC duplex cable (SMF/MMF)
2 MTP-8 to duplex LC breakout module (pinned)
3 8 fibers MTP trunk cable (not pinned)

Figure 6 is also an interconnect solution for SFP+ transceivers, but on the right side an 8-fiber MTP to 4 x LC harness cable and an MTP adapter panel are used instead. This solution works best when connectivity is required for high port count switch.

2-fiber to 2-fiber interconnect (2)

Figure 6: 2-fiber to 2-fiber interconnect (2)

Item Description
1 LC to LC duplex cable (SMF/MMF)
2 MTP-8 to duplex LC breakout module (pinned)
3 8 fibers MTP trunk cable (not pinned)
4 96 fibers MTP adapter panel (8 port)
5 8 fibers MTP (not pinned) to duplex 4 x LC harness cable
Duplex Cross-Connect

This solution is a duplex cross-connect. It will allow all patching to be made at the main distribution area (MDA) with maximum flexibility for port-to-port connection. Figure 7 illustrates the cross-connect solution for duplex connectivity.

2-fiber to 2-fiber cross-connect

Figure 7: 2-fiber to 2-fiber cross-connect

Item Description
1 LC to LC duplex cable (SMF/MMF)
2 MTP-8 to duplex LC breakout module (pinned)
3 8 fibers MTP trunk cable (not pinned)
Parallel Fiber Optic Transmission Links

We will discuss items required to connect two parallel (8-fiber or 20-fiber) transceivers in this part. These protocols include but not limited to: 40GBASE-SR4, 40GBASE-xSR4/cSR4/eSR4, 40GBASE-PLR4, 40GBASE-PSM4, 100GBASE-SR4, 100GBASE-eSR4, 100GBASE-PSM4, 100GBASE-SR10.

Parallel Direct Connectivity (8-fiber or 20-fiber)

When directly connecting two QSFP+ or QSFP 28 transceivers, an 8-fiber MTP trunk cable is needed. For directly connecting two CFP transceivers, a 24-fiber MTP trunk cable is needed.

8-fiber to 8-fiber direct connectivity

Figure 8: 8-fiber to 8-fiber direct connectivity
Parallel Interconnect (8/20-fiber)

Figure 9 shows an interconnect solution for two CFP modules (20-fiber). To break-out the CFPs to transmit the signal across an 8-fiber infrastructure, a 1 x 3 breakout harness (24-fiber MTP to three 8-fiber MTP) is required. To achieve an interconnect for two 8-fiber optics, we can replace the breakout harness by an 8-fiber MTP (pinned) trunk and the 24-fiber MTP trunk by an MTP (not pinned) trunk.

20-fiber to 20-fiber interconnect

Figure 9: 20-fiber to 20-fiber interconnect

Item Description
1 1×3 MTP breakout harness cable (24-fiber MTP to three 8-fiber MTP) (pinned)
2 96 fibers MTP adapter panel (8 ports)
3 24 fibers MTP trunk cable, three 8-fiber legs (not pinned)
Conclusion

This post gives brief introduction to the meaning of duplex and parallel optical link and presents some connectivity solutions for two duplex optics or two parallel optics. The corresponding items used in each solution are listed too. The transmission distance and working environment should be taken into account when applying each cabling solution. The parallel to duplex connectivity solutions will be discussed in the next post.

Basic Knowledge of Fiber Optic Connector

Terminating the end of an optical fiber, the fiber optic connector is utilized to join optical fibers where a connect or disconnect capability is required. A fiber optic connector has three major components: the ferrule, the connector body and the coupling mechanism. Generally made from ceramic, metal or high quality plastic, the ferrule is a thin structure (often cylindrical) that holds the glass fiber. The connector body is a plastic or metal structure that holds the ferrule and attaches to the jacket and strengthens members of the fiber cable itself. And the coupling mechanism is a part of the connector body that holds the connector in place when it gets attached to another device.

Since the fiber cable transmits pulses of light instead of electrical signals, it is important to choose a good fiber optic connector that aligns microscopic glass fibers perfectly in order to allow for communication. Nowadays, there are many different types of fiber optic connectors in the market (as shown in the following figure). Different kinds of optical fiber cables may need different connectors. Seen from the types of optical fiber, the fiber optic connectors may be loosely classified into standard fiber optic connectors, small form factor fiber optic connectors and ribbon fiber connectors. These family types of fiber connectors sometimes may overlap with each other.

fiber optic connector

  • Standard Fiber Optic Connectors

Generally having a ferrule of 2.5 mm, standard fiber optic connectors are connectors commonly used in the fiber network. They can be both simplex and duplex and available in single mode and multi-mode fibers. ST, FC, SC, FDDI and ESCON are all standard fiber connectors. But they also differ from each other. ST connector is the most popular connector for multi-mode fiber optic LAN applications. FC connector is specifically designed for telecommunication applications and provides non-optical disconnect performance. SC connector is widely used in single mode applications for its excellent performance. FDDI connector, which is a duplex multi-mode connector, utilizes two 2.5mm ferrules and is designed to used in FDDI network. ESCON connectors are similar to FDDI connectors, but contain a retractable shroud instead of a fixed shroud.

  • Small Form Factor Fiber Optic Connectors

To meet the demand for devices that can fit into tight spaces and allow denser packing of connections, a number of small form factor fiber optic connectors have been developed since the 1990s. In this type of small form factor fiber optic connectors, some are miniaturized versions of older connectors, built around a 1.25mm ferrule rather than the 2.5mm ferrule. For example, the LC, MU, E2000 connectors. While the others are based on smaller versions of MT-type ferrule for multi-mode fiber connections, or other brand new designs. For example, the MT-RJ connector, which has a miniature two-fiber ferrule with two guide pins parallel to the fibers on the outside. Its overall size is about the same as a RJ45 connector.

  • Ribbon Fiber Connectors

MTP and MPO are compatible ribbon fiber connectors based on MT ferrules which allow quick and reliable connections for up to 12 fibers. Since the MTP product complies with the MPO standard, the MTP connector is an MPO connector. Along with the MTP patch cables (for example, MTP-MTP fiber trunk cable), MTP connectors can upgrade the 10G network to 40G/100G.

The fiber optic connector is an essential part in fiber optical network. As the popularity of fiber optical network, about 100 fiber optic connectors have been introduced to the market. As the main professional fiber optic products supplier in China, Fiberstore offers various kinds of fiber cable connectors, especially the commonly used FC, LC, SC, ST and MPO connectors.

Performance of fiber optic connector

The performance of optical fiber connectors, we should first consideration the optical properties, in addition to considering the interchangeability, repeatability, tensile strength, temperature and mating cycles.

(1) Optical properties: optical performance requirements for fiber optic connectors, mainly insertion loss and return loss of these two basic parameters.
The insertion loss (InsertionLoss) connection loss, refers to the effective optical power loss due to the import of the connector link. Insertion loss as small as possible, the general requirements should not be greater than 0.5dB.
Return Loss (ReturnLoss, ReflectionLoss) refers to the suppression of the connector to link optical power reflection, the typical value should not be less than 25dB. The practical application of the connector, the pin surface after a special polishing allows greater return loss is generally not less than 45dB.

(2) Interchangeability, repeatability
The fiber optic connector is a common passive devices, for the same type of fiber optic connectors, can generally be any combination of uses, and can be used repeatedly, which to import the additional loss is generally in the range of less than 0.2dB.

(3) Tensile strength to do fiber optic connectors, and general requirements for the tensile strength should be not less than 90N.

(4) Temperature
General requirements, fiber optic connectors must be temperature-40oC to 70oC the normal use.

(5) Mating cycles
At present, the fiber optic connectors Can be inserted and pull out over l000 times.

If you want to get more information about fiber optical connectors, please visit the Fiber optic products site.

Several Types of Fast Connectors From FiberStore

FiberStore has developed and dealt with many type of field assembly connectors for many years, the field assembly connectors can be assembled easily and quickly in the field without the additional fiber termination tools, and can be directly connected to drop cable and indoor cable, thus significantly reducing the required work time.

Field assembly connector is a revolutionary field installable optical fiber connector been widely used in passive optical construction field. This connector system doesn’t need any additional assembling tools such as as epoxy, adhesive and costly curing ovens, thus allowing the installer and make new connectors within a mere 3 minutes in the field. It also increasing the flexibility of optical wiring design of FTTH network. The Field assembly connectors have already been widely used in optical distribution cabinet, optical testing instrument and optical transmission network.

FiberStore provide high reliability FC, SC fast connectors in Fiber direct-in type and Preset fiber with matching fluid type, catering for 250um to 900um diameter single mode and multimode fiber types, including Multi-mode 62.5/125um and Multi-mode 50/125um.

Quick Assembly connector SC FC
Quick Assembly SC connector can provide a quick and easy termination of fibers in the field, Both single mode and multi mode connector options are available for 900 micron and 3mm drop cable application, allowing the installer to terminate and make connection in 3 minutes in the field. Special fiber optic crimp tool free design makes it easy in assembling.

Pre-polished Ferrule Field Assembly Connector
Pre-polished ferrule field assembly connector type is a part of optical fiber and has been polished and a pre-polished ferrule and a mechanical splice inside the connector body. The polished ferrule ensures a low insertion loss of the connector. Compare to the direct-in connector, it has a much more stable performance and a longer life time. Our pre-polished ferrule field assembly connectors are now available in FC, SC variants, the single-mode versions are available with PC or APC ferrules.

Without Ferrule Field Assembly Connector
Assembly of the SC, FC type quick connector requires only normal fiber preparation tools: a fiber stripping tool, wipes and a fiber cleaver. No electrical power supply is needed. This fast connectors feature a pre-stubbed factory-polished ferrule that couples to the fiber being terminated. Precision mechanical alignment insures low loss with a proprietary gel.

Cable Mechanical Splicer
Fiber mechanical splicer includes fast fiber optic mechanical splice for 250um bare fiber, MC-L925B optical fiber mechanical splicer, and FTTH drop cable mechanical splicer. Cable mechanical splicer take a global leading submicron processing technology, Use core component of high accuracy V groove provide high alignment, its unique structure had got IPR in 2007. As the first domestic mechanical splicer, the cable mechanical splicer sell well in domestic and abroad market and fill the domestic production of technology and product gaps, cable mechanical splicer have taken great role in FTTH.

Fusion Splice-on Connector
Fusion Splice-on Connector is actually an optical fiber fusion, however the welding point is in the inner end of connector, which makes it no necessary for extra protection equipment, such as fiber protection plate(optical fiber splice tray), optical fiber terminal box, optical fiber distribution frame, after it finished splice fusion. Compared to mechanical optical fast connector, this new practical connector can improve the span life of welding point of connector and reduce maintenance cost.

Besides Fast Connector, we also offer a variety of connector type , including ST, FC, SC, LC, MU, FDDI, E2000 (other connectors types such as OM4 50/125 ST-ST connectors) Fiber Connector etc for Fiber Patch Cord Assembly.

Using Fiber Terminators to Terminator Unused Fiber Connector Ports

With the rapid deployment of high speed fiber multiplexer, the possibility of having an un-terminated derived channel or branch increases. The single fiber connector mated to an unused adapter or coupling is the source of back-reflection. The fiber optic terminator is usually used to terminate the unused fiber connector ports in fiber optic systems. Such unused ports will create unwanted return loss and degrade the whole network performance. Fiber optic terminators are passive components that can absorb light coming from the unterminated connectors plugs and reduce signal degradation in digital and analog systems.

optical terminators
optical terminators from FiberStore

Fiber optic terminators are designed to reduce back-reflections, which is typically found on laser-activated, connectorized access points such as those found on splitters, DWDM’s or fiber distribution frames. are functional devices using Metal-Ion Doped Fibers. By using these fibers, optical terminators can convert the optical power into heat and the power is attenuated inside the devices. The structures of the plug type optical terminators are simple and the power-proof and performance stability is superior. The fiber optic terminators also maintain the cleanliness of unterminated plugs and protect them from possible physical damage.

The plug type optical terminators are used to terminate dark fiber port on the fiber optic component. Their ceramic ferrule is polished with an angled or non-angled end face to reduce unwanted reflections from open ports. These optical terminator also provide improved personal safety over termination methods.

Specifications

Return Loss: UPC >55 dB, APC >65 dB
Back Reflection: APC < -65dB, UPC < -55dB
Temperature Cycling: -20℃~-80℃
Polishing Grade: PC, UPC, APC
Connector Type: SC, FC, ST, LC,MU
Fiber type: SM(9/125㎛)
Optical performance 100% factory tested
Easy installation as plug type
Precision ceramic ferrule with endface
Geometry per IEC proposal
Environmentally stable
Adapt attenuation point to creating termination effect

Applications

Telecommunication Networks
Instrumentation
CATV Networks
Active Device Termination
EDFA

FiberStore provides all types of optical fiber terminators including SC, FC, ST, LC and MU type connector with high precision ceramic ferrule. They can be easily plugged into the systems to significantly reduce reflections from the fiber face, they can also be used with fiber adapters at the male plug end. Besides, FiberStore also provide the mechanical fiber optic termination tools such including fiber optic crimp tool to crimp or connect a connector to the end of a fiber optic cable.