Overview of Single-mode Fiber Types

According to the light transmission mode, optic fibers can be classified into single-mode and multimode. It’s easy to categorize multimode fiber into four types of OM1, OM2, OM3 and OM4. However, when it comes to single-mode, it may not be as simple as you think. The classification of single-mode fiber is much more complicated than multimode fiber. ITU-T G.65x series and IEC 60793-2-50 (published as BS EN 60793-2-50) are two primary sources for single-mode fiber specification. This article will mainly focus on the ITU-T G.65x series.

The following table introduces 19 ITU-T specifications of single-mode fiber:

Name	Type
ITU-T G.652	ITU-T G.652.A, ITU-T G.652.B, ITU-T G.652.C, ITU-T G.652.D
ITU-T G.653	ITU-T G.653.A, ITU-T G.653.B
ITU-T G.654	ITU-T G.654.A, ITU-T G.654.B, ITU-T G.654.C
ITU-T G.655	TU-T G.655.A, ITU-T G.655.B, ITU-T G.655.C, ITU-T G.655.D, ITU-T G.655.E
ITU-T G.656	ITU-T G.656
ITU-T G.657	ITU-T G.657.A, ITU-T G.657.B, ITU-T G.657.C, ITU-T G.657.D

Each type has its own area of application and the evolution of these optical fiber specifications reflects the evolution of transmission system technology from the earliest installation of single-mode optical fiber to the present day. Choosing the right one for your project can be vital in terms of performance, cost, reliability and safety. Now, let’s have a look at the differences of G.65x series specifications for single-mode fiber respectively.

G.652

The ITU-T G.652 fiber is known as standard SMF (single-mode fiber) and is the most commonly deployed fiber. It comes in four variants (A, B, C, D). A and B have a water peak. C and D eliminate the water peak for full spectrum operation. The G.652.A and G.652.B fibers are designed to have a zero-dispersion wavelength near 1310 nm, therefore they are optimized for operation in the 1310nm band. They can also operate in the 1550nm band, but it is not optimized for this region due to the high dispersion. These optical fibers are usually used within LAN, MAN and access network systems. The more recent variants (G.652.C and G.652.D) feature a reduced water peak that allows them to be used in the wavelength region between 1310 nm and 1550 nm supporting Coarse Wavelength Division Multiplexed (CWDM) transmission.

G.653

G.653 fiber was developed to address this conflict between best bandwidth at one wavelength and lowest loss at another. It uses a more complex structure in the core region and a very small core area, and the wavelength of zero chromatic dispersion was shifted up to 1550 nm to coincide with the lowest losses in the fiber. Therefore, G.653 fiber is also called dispersion-shifted fiber (DSF). G.653 has a reduced core size, which is optimized for long-haul single-mode transmission systems using erbium-doped fiber amplifiers (EDFA). However, its high power concentration in the fiber core may generate nonlinear effects. One of the most troublesome, four-wave mixing (FWM), occurs in a Dense Wavelength Division Multiplexed (CWDM) system with zero chromatic dispersion, causing unacceptable crosstalk and interference between channels.

G.654

The G.654 specifications entitled “characteristics of a cut-off shifted single-mode optical fiber and cable”. It uses a larger core size made from pure silica to achieve the same long-haul performance with low attenuation in the 1550nm band. It usually also has high chromatic dispersion at 1550 nm, but is not designed to operate at 1310 nm at all. G.654 fiber can handle higher power levels between 1500 nm and 1600 nm, which is mainly designed for extended long-haul undersea applications.

G.655

G.655 is known as non-zero dispersion-shifted fiber (NZDSF). It has a small, controlled amount of chromatic dispersion in the C-band (1530-1560 nm), where amplifiers work best, and has a larger core area than G.653 fiber. NZDSF fiber overcomes problems associated with four-wave mixing and other nonlinear effects by moving the zero-dispersion wavelength outside the 1550nm operating window. There are two types of NZDSF, known as (-D)NZDSF and (+D)NZDSF. They have respectively a negative and positive slope versus wavelength. Following picture depicts the dispersion properties of the four main single-mode fiber types. The typical chromatic dispersion of a G.652 compliant fiber is 17ps/nm/km. G.655 fibers were mainly used to support long-haul systems that use DWDM transmission.

G.656

As well as fibers that work well across a range of wavelengths, some are designed to work best at specific wavelengths. This is the G.656, which is also called Medium Dispersion Fiber (MDF). It is designed for local access and long haul fiber that performs well at 1460 nm and 1625 nm. This kind of fiber was developed to support long-haul systems that use CWDM and DWDM transmission over the specified wavelength range. And at the same time, it allows the easier deployment of CWDM in metropolitan areas, and increases the capacity of fiber in DWDM systems.

G.657

G.657 optical fibers are intended to be compatible with the G.652 optical fibers but have differing bend sensitivity performance. It is designed to allow fibers to bend, without affecting performance. This is achieved through an optical trench that reflects stray light back into the core, rather than it being lost in the cladding, enabling greater bending of the fiber. As we all know, in cable TV and FTTH industries, it is hard to control bend radius in the field. G.657 is the latest standard for FTTH applications, and, along with G.652 is the most commonly used in last drop fiber networks.

Conclusion

There are different types of single-mode fiber used for different application. G.657 and G.652 are typically favored by planners and installers, and G.657 is particularly deployed for FTTH applications because of a larger bend radius. And G.655 has been taken the place of G.643 used for WDM system. In addition, G.654 is usually applied to the subsea area. To know more information about single-mode fiber, you are welcome to visit the website at FS.COM.

The article originates from http://www.fiber-optic-cable-sale.com/overview-of-single-mode-fiber-types.html.

Comparison Between MMF and SMF Optical Cables

According to different standards, fiber optic cables can be categorized into different classifications. One way is to classify the cable into single-mode fiber (SMF) and multimode fiber (MMF). The comparison between these two types of optical cables can assist you in choosing the most suitable cable for device. This article will compare the two kinds of cables from cable path, distance, precision termination, cost and color. Hope you can find some useful information from the article.

Single Path Vs. Multiple Paths

SMF uses laser light which usually follows a single path through the fiber. MMF takes multiple paths, which may result in a differential mode delay. Each type of fiber can be applied for different equipment. It’s important to know which application is more suitable for practical use. Otherwise, it will not operate at optimal levels.

Short Distances Vs. Long Distances

SMF is used for long distance communication, and MMF is used for distances of 500m or less. Each type is equally as effective when chosen for the proper communication device. Make sure to check the ratings to determine which type is best for your application. The distances should be clearly marked.

Thick Core Size Vs. Thin Core Size

SMF typically has a smaller core size of 8.3 to 10 microns in diameter which is more precise for signal transmission in long distance, while the core size of MMF is much larger than SMF from 50 to100 microns in diameter which is more suitable for short distance transmission owing to the signal distortion. With a thinner core size, SMF is only allowed to carry a single light-wave along a single path, while the thick core size makes MMF able to carry different light-waves along numerous paths without modal dispersion limitation.

Low Cost Vs. High Cost

MMF is typically a lower cost solution than SMF. Limited budget may prompt designers to seek solutions with MMF fiber optic cables. The equipment that’s used for communications over MMF is usually less expensive than SMF. But the typical transmission speed and distance of MMF have limitations of 100 Mbit/s for distances up to 2 km.

Color Differences

MMF and SMF cables can also be distinguished by color. Usually, yellow is used for SMF cable color and orange or aqua is used for MMF cables. It is much easier to distinguish them just by their appearance color.

Other Primary Differences

MMF is typically characterized by having a larger core diameter. In most cases, it’s larger than the wavelength of light it supports. Therefore, MMF has more capacity to gather light than SMF. A larger core size means that designers can create a lower cost electronic device and offer a lower price to the public. Also, by using light-emitting diodes (LEDs) and vertical-cavity surface-emitting lasers (VCSELs), the costs can be driven down even more.

Conclusion

SMF and MMF are two different optic cables which have their own separate application fields. It is terribly wrong for not selecting suitable SMF or MMF patch cables according to the application. Think twice before you are certain that the cable is the best choice for your project. If you want to know more details about SMF and MMF fiber optic cables, FS.COM can solve all your problems.

The article originates from http://www.fiber-optic-cable-sale.com/comparison-between-mmf-and-smf-optical-cables.html.

Reasons for Choosing Optic Fiber Over Copper Cable

 Nowadays, facilities like studios and control rooms are being upgraded to support the 4G or even 5G networks. This calls for fiber-based infrastructures to support the higher data rates. Optic fiber can provide substantial advantages of high performance over longer distances, virtually unlimited bandwidth, reduced sensitivity to electrical interference, lower cost and design of greater space and lighter weight. These benefits make optic fiber much better than the average copper cable. Followings are some specifically explanatory reasons for choosing optic fiber over copper cable.

 Firstly, the virtually unlimited bandwidth of optical fiber is better than the bandwidth limit of copper coaxial cable (coax). With a relatively low attenuation, the unlimited bandwidth is able to produce some rather surprising increases in capacity and range. Here’s an example, some fiber optic product combinations can reach the link length of more than 100km while a copper cable can only handle 3G for up to 75m. It can also carry multiple signals and a wide range of signal formats in a single cable. Moreover, the virtually unlimited bandwidth makes it possible for optic fibers to transmit bidirectional wavelengths with one in the forward direction and another in the reverse direction. 

 Secondly, the cost of fiber is not that expensive as it was before. In general, fiber cable is more expensive than copper cable in the short run, but it may be less expensive in the long run. The typical published price in the US for a single core PVC jacketed single-mode fiber is even cheaper than broadcast quality coax cable, suitable for HD-SDI, thus it is not a dream to make the cost of other optic fibers less than the cost of copper cable in the future. When transmitting the different signal types of digital systems, for instance, two video signals with four channels of audio, this benefit is required to make the digital systems affordable for people. In a word, bandwidth costs money, and fiber offers a way to minimize these costs. 

 Thirdly, the design of size and weight of the optic fiber is better than the copper cable. For example, a 2.9mm single core fiber weighs about 9 grams per meter, but a 1694A coax is about 61 grams per meter which is over six and a half times heavier than optic fiber. This kind of advantage is especially benefit for production trucks or OB vans which can solve the tight space and weight problems.

 From the discussion above, we may have a general understanding of why we should choose optic fiber rather than copper cable. In addition, there are also some ways for easier fiber transition. 

 One is the using of Small Form-factor Pluggable (SFP) fiber optic transceiver. SFP fiber modules are small, hot-pluggable devices used to provide fiber connectivity to 3G/HD/SD devices. The single-mode SFP fiber optic transceiver helps devices to be used over long range without degrading signal quality. The most important benefit is that SFP simplifies the migration to fiber. 

 Another method is the utilizing of CWDM fiber. It is ideally used to meet the demand of carrying multiple and different signals across long distances, either building-to-building or truck-to-truck. The CWDM MUX unit can combine at most 18 different wavelengths into a single optical fiber, and it is the same for CWDM DEMUX in reverse. Signal types are irrelevant to these units, thus different signals like AES, MADI, DVB-ASI, 3G/HD/SD-SDI or Ethernet can travel on the same fiber link. 

 To sum up, the benefits of choosing optic fiber are more than choosing copper cable. Because fiber cable costs less than it was once, becomes physically smaller, and weighs less. Also, compared to one copper coax, a single fiber is available to carry 18 full 3G signals, and a fiber signal path can be 500 to 1000 times longer than that of copper coax. From a system design, installation and maintenance perspective, the application of SFP fiber and CWDM fiber also helps a simpler proposition for optic fiber cable. Hence, optic fiber is highly recommended to be used in all broadcast facilities, as well as at pay TV operator networks. Optic fiber is a better choice for everyone.