Single Mode Fiber Type: G652 vs G655 Fiber

With the increasing demand for greater capacity over long distance transmission, single mode fiber optic cable is designed with various versions. There are 6 different categories of SMFs: G652, G653, G654, G655, G656 and G657, among which G652 and G655 are two options frequently used in WDM. So G652 vs G655 fiber: what’s the difference?

Single Mode Fiber: What Is G652?

G652 is currently the most popularly adopted single mode fiber, for which G652 is defined as Standard SMF. It has G652A, B, C and D four versions. G652A and B have a zero dispersion wavelength point at 1310 nm, which makes it a natural fit for operation in the 1310 nm band. However, they are not suitable for applications in Wavelength Division Multiplexing (WDM) due to water peak. The more advanced C and D are optimized with elimination of water peak for spectrum operation, which makes them effective at wavelength between 1310 to 1550 nm to support Coarse Wavelength Division Multiplexing (CWDM). Comparing G652C, G652D single mode fiber has superior PDM (polarization mode dispersion) parameter, for which G652D is known as Standard single mode fiber (SSMF) and commonly used to support 10GbE and 40GbE system. FS. COM provides such G652D LC fiber in various versions.

FS.COM G652D LC single mode fiber single mode fiber

Figure 1: This photo shows a FS.COM G652D LC single mode fiber.

Single Mode Fiber: What Is G655?

G655 is known as nonzero dispersion-shifted fiber (NZDSF), because the dispersion at the wavelength of 1550 nm is close to zero but not zero. It is further divided into A, B and C three subcategories. There are two types of NZDSF: (+D)NZDSF and (-D)NZDSF, the dispersion of which is respectively proportional and inversely proportional to wavelength. Among them, the positive dispersion of G655 overcomes nonlinear effects in WDM system such as four wave mixing (FWM) due to high effective area. G655 is specified at 1550 nm and 1620 nm, and has low value of chromatic dispersion in the c-band (1530 -1660 nm), in which Erbium Doped Fiber Amplifier (EDFA) boost the optical signals. This match gives G655 an edge over G652. G655 fiber is suitable for DWDM system to meet increasing transmission capacity and long haul high capacity WDM transmission system.

Difference of G652 vs G655 single mode fiber

Figure 2: This diagram shows the difference of G652 vs G655.

G652 vs G655 Single Mode Fiber: What’s the Difference?

Table below shows the detail information of G652 vs G655 fiber.

Fiber Type G652 G655
Alternative Name Standard SMF/zero dispersion-shifted fiber (non dispersion-shifted fiber) Nonzero dispersion-shifted fiber (NZDSF)
Specified Wavelength 1310, 1550, 1625 nm (C and D excluded) 1550-1625 nm
Dispersion Point 1310 nm 1550 nm
Dispersion Value Higher Low
Attenuation Parameter Less than 0.4 dB/km Typically 0.2 dB/km at 1550 nm
PMD Parameter Less than 0.5 over C and 0.2 over D Less than 0.1 ps/sqrt (km)
Applications LAN, MAN, access networks and CWDM transmission Long-haul systems that use DWDM transmission
Price Lower than G655 High
Features Reduced water peak Low dispersion value; overcoming nonlinear effect

As shown in the table, G652 and G655 fiber are two single mode fiber types defined with different specifications of wavelength, dispersion, parameter of attenuation and PMD. G652 is featured a zero dispersion wavelength at 1310 and reduced water peak to support CWDM. G655 is an enhanced single mode fiber with the characteristic of elimination of FWM and low dispersion value, typically applied to long and high-speed DWDM transmission. For consideration of both the function and price, G652 especially G652D version has become the most commonly used one.

Conclusion

This article introduced two categories of single mode fiber types and made a contrast between G652 vs G655. It’s not proper to say one type beats the other since both have their characteristics for different applications. For transmission not requiring very high rate and long distance, G652. D can be the choice. But for much higher capacity and long distance required DWDM system, G655 will best meet the needs regardless of much higher cost.

A Brief Overview of Fiber Optic Cable

Introduction

A fiber optic cable, also known as optical fiber cable, is a network cable that contains two or more glass or plastic fiber cores located within a protective coating and covered with a plastic PVC outer sleeve. It’s correlated with transmission of information as light pulses along a glass or plastic strand or fiber. It’s designed for long distance, very high performance data networking and telecommunications. It has many advantages in optical fiber communication, such as large capacity, long relay distance, good security, free from electromagnetic interference and copper saving.

fiber- optic- cable

Types of Fiber Optic Cables

According to the transmission mode of light in optical fiber, fiber optic cable can be divided into single-mode fiber (SMF) and multimode fiber (MMF). Although they all belong to optical cables and aim at transmitting information, they still have some slight differences.

SMF & MMF

Single-Mode Fiber

Literally, Single-mode fiber is a single stand of glass fiber with a diameter of 8.3 to 10 microns that has one mode of transmission. Due to its smaller diameter, single-mode fiber is used for long-distance signal transmission, which minimizes the reduction in signal strength. Single-mode fiber also has a considerably higher bandwidth than multimode fiber. The light source used for single-mode fiber is typically a laser, which makes it more expensive than multimode fiber.

Multimode Fiber

By comparison, multimode fiber cable, with a diameter of about 62.5 microns, allows multiple mode of light to propagate through it simultaneously, thus forming mode dispersion. Mode dispersion technology limits the bandwidth and distance of multimode fiber. Therefore, multimode fiber features larger core diameter and short transmission distance. Multimode fiber typically uses an LED to create the light pulse, which makes it cheaper than single-mode fiber.

Both single-mode and multimode fiber can handle 10G speeds. The most evident difference between them lies in the distance. Within a data center, it’s typical to use multimode fiber which can get you 300-400 meters. If you have very long runs or are connecting over longer distance, single-mode fiber can get you 10 km, 40 km, 80 km, or even farther. You just need to use the appropriate optic for the distance required.

Fiber Cable Uses

It’s widely acknowledged that optical cables are usually applied into computer networking and telecommunication due to its ability to transmit data and information. What’s more, it’s also used by military and space industries as means of communication and signal transfer, in addition to its ability to provide temperature sensing. In recent years, fiber cable is frequently used in a variety of medical instruments to provide precise illumination. An endoscope, for example, is a flexible tube containing several optical cables. When it slips into the patient’s mouth, nose, digestive tract, and other heart areas that are not visible outside the body, the doctor can see the changes through the endoscope. Other medical applications for fiber optics include X-ray imaging, biomedical sensors, light therapy and surgical microscopy.

Conclusion

From the aforementioned article, we can see that fiber optic cables have different types with different features, and are widely used in telecommunication, military, medical applications, etc. If you would like to know more or would like assistance in choosing the appropriate optical fiber cable, welcome to visit our website www.fs.com for more detailed information. FS will provide more choices and better services for our clients.

Introduction to Fiber Optic Pigtails

During the process of fiber optic cable installation, cable connection is important to ensure the low attenuation and low return loss of signal transmission between cable and equipment. And fiber optic pigtail is a commonly used component for the connection of optical network. It is a piece of cable terminated with fiber optic connectors at one end and no connector at the other end. In this way, the connector side can be linked to the equipment and the other side can be fused with optical cable fibers. This article will emphasize on the types of fiber optic pigtails and their applications.

Here are two classifications of fiber optic pigtails. Firstly classified by connectors, fiber optic pigtails has seven types including E2000, LC, SC, ST, FC, MU and MTRJ. Secondly classified by fibers, fiber optic pigtails has two types as single-mode and multimode.

Classification of Connector

LC-fiber-optic-pigtail

1)LC fiber optic pigtail uses the LC connector developed by Lucent Company. LC connector is now one of the most popular connectors in the world. A 1.25mm ceramic ferrule makes LC fiber optic pigtail a better choice for low cost but high precision signal transmission.

SC-fiber-optic-pigtail

2) SC fiber optic pigtail uses the SC connector developed by Nippon Telegraph and Telephone. SC connector has a ceramic ferrule of 2.5 mm. Its light weight and cost-effective features enable different applications of SC fiber optic pigtail.

 

ST-fiber-optic-pigtail

3)ST fiber optic pigtail uses the ST connector developed by American Telephone & Telegraph. ST connector has a 2.5mm bayonet-styled ferrule. It is one of the eldest generations of fiber optic connectors. But it is still used for many fiber optic applications, especially for multimode fiber optic communications.

FC-fiber-optic-pigtail

4)FC fiber optic pigtail uses the FC connector developed by Nippon Electric Company. The connector features the screw type structure and high precision ceramic ferrule. FC fiber optic pigtail is usually used for general fiber optic applications.

 

Classification of Fiber Types

Single-mode fiber and multimode fiber are both used for fiber optic pigtails. The single-mode fiber optic pigtail has a 9/125 micron core size. SC, LC, ST, FC and E2000 connectors are all fit for this kind of fiber. As for multimode fiber optic pigtails, there are two different core sizes. One is 62.5/125 micron of OM1, and the other is 50/125 micron of OM2, OM3, OM4. SC, LC, ST, FC connectors are adaptable to multimode fiber optic pigtails.

Applications

Fiber optic pigtail sometimes has multiple fiber strands, including 4 fibers, 6 fibers, 8 fibers, 12 fibers, 24 fibers, 48 fibers and so on. This helps the effective interconnection and cross-connect in various applications. Since fiber optic pigtail supports fusion splicing, it is often used with devices like optical distribution frames, splice closures and cross cabinets.

Conclusion

In summary, fiber optic pigtail is a cable that only one end is terminated with connectors. The other end can be melted with optical fiber for a permanent connection. You may choose the adaptable fiber optic pigtail from the perspective of connector types, fiber types, strand numbers, etc. Hope this article can provide a little help.

Next-Generation OM3 Multimode Fiber

We know that conventional datacom links use single-mode fiber (SMF) for long-distance, high-speed links and multimode fiber (MMF) for shorter links. Early datacom applications, including ESCON, Token Ring, FDDI, Ethernet, and ATM, operated at relatively slow data rates (4-155 Mbit/s), using low-cost infrared light-emitting diode transmitters (LEDs). And this article will focus on OM3 multimode fiber.

The Development of MMF

The earliest fibers, called Optical Multimode 1 (OM1), featured a large core than is used today and a bigger numercial aperture. As the technology matured, smaller core MMF was typically rated for a minimum bandwidth-distance product around 160 MHz*km for 62.5/125 micron fiber at 850 nm wavelength; 500 MHz*km for 50/125 micron fiber at this wavelength; and 500 MHz*km for both fiber types at 1300 nm wavelength. This fiber was compatible with various industry standards, including CCTIT recommendation G.652, and was defined by the ISO standards as “optical multimode 2” (OM2) fiber; it is also commonly known as “FDDI grade” fiber, The fiber bandwidth was measured using an overfilled launch (OFL) test procedure, which replicated the large spot size and uniform power profile of a LED. Since a LED consistently fills the entire fiber core, the fiber bandwidth is determined by the aggregate performance of all the excited modes. However, LED sources typically have a maximum modulation rate of a few hundred Mbit/s; with the growing demand for higher data rates, laser sources operating over SMF were required.

Issues Related to VCSELs

Single-mode links using Fabry-Perot or distributed feedback lasers operating at long wavelength (1300nm) tend to be higher cost due to their tighter alignment tolerances and higher performance characteristics. There is lower cost alternative; the recent deployment of short-wave (780-850 nm) vertical cavity surface emitting lasers (VCSELs) has made it possible to use MMF at higher data rates over longer distance. Compared with LEDs, VCSELs offer higher optical power, narrower width, smaller spot size, less uniform power profiles, and higher modulation data rates. This means that a VCSELs will not excite all of the modes in a MMF; the fiber bandwidth is determined by a restricted set of modes, typically concentrated near the center of the core. Older MMFs experienced significant, often unpredictable variations in bandwidth when used with VCSEL sources due to defects or refractive index variations in the fiber core and variations in the number and power of excited modes due to fluctuations in the VCSEL output or between different VCSEL transmitters.

In response to these problem, the datacom industry developed a new type of laser-optimized or laser-enhanced MMF specifically designed to achieve improved, more reliable performance with VCESLs. Precise control of the refractive index profile minimizes modal dispersion and differential mode delay (DMD) with laser sources, while remaining backward compatible with LED sources (the dimensions, attenuation, and termination methods for laser-optimized and conventional fiber are the same). The first laser-optimized fibers, introduced in the mid-1990s, were available in both 50-microns and 62.5-micron varieties and designed for 1-Gbit/s operation up to a few hundred meters. These fibers were not always capable of scaling to higher data rates; with the increased attention on 10-Gbit/s links, never types of reaching about 35 meters at 10-Gbit/s, it became apparent that the smaller core diameter and reduced number of modes in 50 micron fiber made it the preferred choice for these data rates. Today, laser-optimized fiber is commonly available only in 50-micron versions, with an effective bandwidth-distance product around 2000 MHz*km for 850 nm laser sources. The bandwidth must be measured using a restricted mode launch (RML) test, instead of the conventional OFL method. This fiber was defined in the TLA-568 standard as “laser-optimized multimode fiber, ” and in the ISO 11801 (2nd edition) by its more common name, “optical multimode3” (OM3) fiber. Click to buy OM3 fiber patch cables.

Colors of Fiber Cables

An early example of laser-optimized fiber is the Systimax Lazer SPEED fiber introduced by Lucent, which uses a green jacket to distinguish it from existing multimode (orange) , single-mode (yellow) , and dispersion-managed (purple) fiber cables. Attenuation is about 3.5 dB/km at 850 nm and 1.5 dB/km at 1300 nm; bandwidth is 2200 MHz*km at 850 nm (500 MHz*km overfilled) and 500 MHz*km at 1300 nm (no change when overfilled) . Another example is the Corning Infini-Core fiber, which typically uses an aqua-colored cable; the CL 1000 line consists of 62.5-micron fiber made with an outside vapor deposition process that achieves 500-m distances at 850 nm and 1 km at 1300 nm. Similarly, the CL 2000 line of 50-micron fiber supports 600-m distances at 850 nm and 2 km at 1300 nm. Here is a figure of OM3 multimode fiber for you.

OM3 multimode fiber

Applications of OM3

Most recent installations of Ethernet, Fibre Channel, InifiniBand, and other systems use the preferred OM3 multimode fiber (for example, the OM3 SC to LC), and many legacy systems including ESCON are compatible with this fiber. In order to avoid the associated with installing new fiber, most standards attempt to accommodate various types of MMF. While the idea of backward compatibility works reasonably well up to 1 Gbit/s (distances of a few hundred meters can be achieved) , it begins to break down at higher data rates when the achievable distance is reduced even further. Designing a future-proof cable infrastructure under these conditions becomes increasingly difficult; at some point, new fiber needs to replace the legacy MMF. Although SMF should be a good long-term investment, the short-term cost premium for SMF installation and ports on many switches, servers, and storage devices remains a concern. Since the cost of short-wave transceivers is presently lower than long-wave transceivers, there is still some question as to the preferred fiber to install and the best mixture of 62.5-micron and 50-micron MMF. In general, 50-micron fiber has been widely deployed in Europe and Japen, while North America has primarily used 62.5-micron MMF until recently. The IEEE has recommended using 62.5-micron MMF in building backbones for distances up to 100m, and 50-micron fiber for distances between 100 and 300 m.

Conclusion

Mixing OM2 and OM3 fibers in the same link results in an aggregate bandwidth proportional to the weighted average of the two cable types. Care must be taken not to mix 50-and 62.5-micron fibers in the same cable plant, as the resulting mismatch in core size and numerical aperture creates high losses. This can make it difficult to administer a mixed cable plant, as there is no industry standard connector keying to prevent misplugging different types of MMF into the wrong location.

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