Advice on Patch Cable Selection for Optical Transceiver

Fiber optic network connection can’t be achieved without fiber optic transceivers and fiber patch cables. Fiber optic transceivers vary from transmission media, interface, transmission distance, data rate, and brand, for example, SFP for 1000Mbps, SFP+ for 10G, QSFP+ for 40G, CFP and QSFP28 for 100G. It’s not difficult to identify these transceivers. But when you connect the transceiver to the patch cable, many details need to be noticed. This article will give you advice on how to choose the suitable patch cable for your transceivers.

Transmission Media—Copper & Fiber

According to transmission media of fiber optic and copper, transceivers can be divided into two kinds, copper based transceivers and fiber optic based transceivers. MSA has defined several copper based transceiver like: 100BASE-T, 1000BASE-T and 10GBASE-T. Copper transceivers are available in GBIC, SFP and SFP+ form factors, which usually has a RJ45 interface. So Cat5/6/7 cables are typically used to connect with the transceivers. Maybe Cat8 will be researched and developed to support higher data rate up to 40G sooner or later.

As to fiber optic transceivers, things are more complex. For that fiber optic transceivers require different fiber patch cords which have more types. Fiber patch cables cover single-mode and multimode. Single-mode patch cable can be classified into OS1 and OS2. While multimode cables can be divided into OM1, OM2, OM3, OM4 cable. Different cables are used in different applications. Single-mode cable can support long distance transmission and multimode cable for short distance link. If the transmission distance is shorter than 500 meters, multimode patch cable is suggested. For long distance transmission, single-mode transmission is suggested. You should also consider that the transmission data rate can also affect the transmission distance. Let’s look at the following point.

Supported Distance and Data Rate

MSA has defined a variety of transceivers that can support different transmission distances and data rates. When you buy a fiber optic transceiver, you will find the data rate, wavelength, distance, etc. on its labeling. The following table show the basic information of most often used transceivers and supported cable type.

Description	Wavelengh	Data Rate	Cable Type	Distance
SX	850nm	1G	MM	500 m
LX	1310nm	1G	SM	8 km
EX	1310nm	1G	SM	40 km
ZX	1550nm	1G	SM	70 km
SR	850nm	10G	MM	300 m
LR	1310nm	10G	SM	10 km
ER	1550nm	10G	SM	40 km
ZR	1550nm	10G	SM	80 km
SR4	850nm	40G	MM	100 m
SR10	850nm	100G	MM	100 m
LR4	1310nm	40G	SM	10 km

As mentioned before, single-mode patch cable is better for long distance transmission and multimode patch cable for short distance transmission. Actually single-mode patch cords can be used for different data rates in both long and short distances. But single-mode fiber optic cable will cost more. To achieve reliable performance in short distances with cost effective solutions, you should know the performance of multimode fiber optic cables. The following chart provides the detailed transmission distances and data rates information for different multimode fiber optic cables over wavelength of 850 nm for your reference.

Fiber Type	1G	10G	40/100G
OM1	300 m	36 m	N/A
OM2	500 m	86 m	N/A
OM3	1 km	300 m	100 m
OM4	1 km	550 m	150 m

Transceiver Interfaces

The selection of patch cable for transceiver should also consider the interfaces through which patch cords is connected to the transceiver. In addition, transceiver usually used one port for transmitting and one port for receiving. Generally, fiber optic transceivers usually employs duplex SC or LC interfaces. However, for BiDi transceivers only one port is used for both transmitting and receiving. Thus, simplex patch cord is used with BiDi transceiver.

Some 40G/100GBASE QSFP+ transceivers used MTP/MPO interfaces, which should be connected to the network with multi-fiber patch cords attached with MTP/MPO connectors. If these ports are used for 40G to 10G or 100G to 10G connection, then fanout patch cable should be used. For example, a MTP to 8 LC fanout cable can splitter 40G data rate to four 10G data rate.

Summary

Next time when you select patch cords for your fiber optic transceivers, you can consider these factors like transmission media, transmission data rate and distance, transceiver interfaces. FS.COM offers a wide range of fiber optic transceivers and patch cords. Custom service is also available. Any problem, please contact us via sales@fs.com.

Originally published at www.fiber-optic-equipment.com

Optical Fiber Selection for Network Interconnection

The emergence of Data Centers, Storage Area Networks and other computing applications drives the needs for ultra-high speed data interconnections and structured cabling. The interconnect media choices include wireless technology, copper cable and optical fiber cable. Fiber cable offers the highest bandwidth and supports the highest data rates. There are single-mode and multimode fiber types. Different types of fiber connect with fiber optic transceivers resulting in different performances and costs. So it’s important for the network designers to understand the fiber types and select the right fiber and corresponding fiber optic transceivers for network interconnection.

Optical Fiber Types

There are three main types of optical fiber suitable for network interconnection use:
9/125μm Single-mode fiber
50/125μm multimode fiber
62.5/125μm multimode fiber

The above numbers respectively mean the diameter of the glass core where the light travels and outside glass cladding diameter which is almost the same to most fiber types. So the difference of each fiber type is caused by the core diameter. It has great impact on system performance and system cost when balanced against network application needs. Two primary affected factors are attenuation and bandwidth.

Factors Affected by the Fiber Core Diameter

Attenuation is the reduction of signal power, or loss, as light travels through an optical fiber. Fiber attenuation is measured in decibels per kilometer (dB/km). The higher the attenuation, the higher rate of signal loss of a given fiber length. Single-mode fibers generally operate at 1310 nm (for short range) while multimode fibers operate at 850 nm or 1300 nm. Attenuation is not usually considered to be the main limiting factor in short rang transmissions. But it can cause big differences in high speed network such as 100Gb/s.

Bandwidth means the carrying capacity of fiber. For single-mode fiber, the modal dispersion can be ignored since its small core diameter. Bandwidth behavior of multimode fibers is caused by multi-modal dispersion during the light traveling along different paths in the core of the fiber. It has an influence on the system performance and data rate handling. Multimode fiber uses a graded index profile to minimize modal dispersion. This design maximizes bandwidth while maintaining larger core diameters for simplified assembly, connectivity and low cost. So manufacturers start to develop higher-performance multimode fiber systems with higher bandwidth.

System Costs: Single-mode and Multimode Fibers

A fiber optic transceiver usually consists the optical light sources, typically LED–light emitting diode and optical receivers. Since the core diameter size and primary operating wavelengths of single-mode fiber and multimode fiber are different, the associated transceiver technology and connectivity will also be different. So is the system cost.

To utilize the single-mode fibers generally for long distance applications (multi-kilometer reach), transceivers with lasers such as SFPP-10GE-LR (an SFP+ 1310nm 10 km transceiver supporting single-mode fibers) that operate at longer wavelengths with smaller spot-size and narrower spectral width. But these kinds of transceivers need higher precision alignment and tighter connector tolerance to smaller core diameters. Thus, it causes higher costs for single-mode fiber interconnections. To lower the cost, manufacturers produce transceivers based on VCSEL (vertical cavity surface emitting laser), for example, 10G-SFPP-SR (an SFP+ 850nm 300m transceiver supporting multimode fibers), which are optimized for use with multimode fibers. Transceivers applying low cost VCSEL technology to develop for 50/125μm multimode fibers, take advantage of the larger core diameter to gain high coupling efficiency and wider geometrical tolerances. OM3 and OM4 multimode fibers offer high bandwidth to support data rates from 10Mb/s to 100Gb/s.

Conclusion

Optical fiber is an easily-installed medium that is immune to electromagnetic interface and is also more efficient in terms of power consumption. What’s more, fiber optic cable can save space and cost with higher cabling density and port density over copper cabling. For single-mode fiber and multimode fiber, each one has its advantages and disadvantages. Network designers should better select the right fiber type and related fiber optic transceivers according to specific situations for higher system performance. Of course, cost is another important factor to be considered.

Originally published at www.fiber-optic-equipment.com