Loose-Tube VS. Tight-Buffered Fiber Optic Cable

It is known that fiber optic cable has been the preferred medium for the data center backbone due to channel capacity and scalability, total immunity to electromagnetic interference (EMI) and radio frequency interference (RFI), elimination of the crosstalk inherent in copper cabling (like twinax cable), smaller diameter, and ease of installation, particularly when using pre-terminated modular trunk cables. Selecting the right type of fiber optic cable boils down to the applications and the installation. This post will introduce and compare two fiber optic cable types based on different cable constructions—loose-tube and tight-buffered fiber optic cable.

Loose-Tube Fiber Optic Cable Overview

In loose-tube construction, the fiber is laid helically into semi-rigid tubes, allowing the cable to stretch without stretching the fiber itself, which can protect the fiber from tension during laying and due to temperature changes. Loose-tube fiber may be “dry block” or gel-filled. Dry block offers less protection to the fiber than gel-filled, but costs considerably less. Loose-tube fiber cable comes in various fiber counts that typically range from 6 to 144, with some manufacturers offering higher counts up to 216 fibers. Except a 6-fiber cable, the fibers are grouped into sets of 12 for maximum density.

Structure of Loose-Tube Cable

The following image shows the main components used to construct a Loose-tube cable.

• Multiple 250um coated bare fibers in loose tube.
• One or more loose tubes holding 250um bare fibers. Loose tube stranded around the central strength member.
• Moisture blocking gel in each loose tube for water blocking and protection of 250um fibers.
• Central strength member in the center of the cable and is stranded around by loose tubes.
• Aramid Yarn as strength member.
• Ripcord for easy removal of outer jacket.
• Outer jacket(PVC is most common for outdoor cables because of its moisture resistant, abrasion resistant and stable over wide temperature range characteristics).

Advantages of Loose-Tube Cable

• Extreme Temperature Resistant: Loose-tube cable establishes a strain-free environment for the optical fiber by mitigating the influence of external effects, which makes it perform well at extreme temperatures. Besides, this characteristic also enhances the performance of the loose-tube cable design under a variety of mechanical forces, such as tensile, flexure, twisting, crush, etc.
• Water-blocking Characteristic: As we all know, the core fiber of loose-tube cable is surrounded with a dry water-swellable tape and yarns, or with a gel, which can effectively stop the entry and migration of water.
• UV Protection: The outer jacket of loose-tube cable consists of carbon black, which can provide maximum ultraviolet protection, making the cable able to withstand direct exposure to ultraviolet sunlight in aerial installations.

Tight-Buffered Fiber Optic Cable Overview

Instead of a loose tube, the fiber may be embedded in a heavy polymer jacket, commonly called “tight buffer” construction. Tight-buffered cables are offered for a variety of applications, but the two most common are “breakout” and “distribution”. Tight-buffered cable comes in fiber counts ranging from 2 to 144 fibers, with larger fiber counts featuring fiber subunits of 6 or 12 fibers within the cable. For example, a 144-fiber cable usually has twelve 12-fiber subunits while a 36-fiber cable could have six 6-fiber subunits or three 12-fiber subunits.

Structure of Tight-Buffered Cable

The following image shows the structure of tight-buffered cable.

• Multiple 900um tight-buffered fibers stranded around the central strength member.
• Central strength member in the center of the cable.
• Aramid Yarn(trade name Kevlar) wrapped around the fibers for physical protection and cable pulling.
• Ripcord for easy removal of outer jacket.
• Outer jacket or sheath(usually PVC).

Advantages of Tight-Buffered Cable

• Easy to Install: Tight-buffered cables are easier to install, because there is no messy gel to clean up and they don’t require a fan-out kit for splicing or termination. You can crimp connections directly to each fiber.
• Higher Survivability Standard: Based on military technology for survival under mechanical and environmental stresses.
• Flexibility: No stiff strength member is needed, making the cable more flexible. The cable is also “tight bound” allowing it to be pulled around multiple bends or hung vertically without causing “fiber axial migration”.

Which One to Choose—Loose-Tube or Tight-Buffered?

After we have introduced these two types of fiber optic cables, people may wonder which one is the best for their project. Actually, these two cable types are deployed in different applications.

Loose-tube cable is specifically designed for harsh environments. It has a water-resistant gel that surrounds the fibers, which helps the fibers from moisture, making the cable ideal for harsh, high-humidity environments where water or condensation can be a problem. The gel-filled tubes can also expand and contract with temperature changes. Loose-tube cable has a higher tensile strength than tight-buffered cable. But it is not the best choice when cable needs to be routed around multiple bends, which is often true in indoor applications. Excess cable strain can force fibers to emerge from the gel.

Tight-buffered cable is optimized for indoor applications. Because it’s sturdier than loose-tube cable, it is more available for moderate-length LAN/WAN connections or long indoor runs, and even direct burial. Tight-buffered cable is also recommended for underwater applications.

Summary

Choose the right cable types for your applications can effectively improve network performance and ensure the life span of the whole project. FS.COM offers a wide range of loose-tube and tight-buffered cables in different fiber counts and with single-mode fiber or multimode fiber. For more detailed information, please visit FS.COM.

Why We Choose Fiber Cable over Copper Cable?

When selecting networking cable for your project, fiber cable or copper cable as shown below, which one do you prefer? Actually, both of them have advantages and specific features. Copper cable has already existed in many places and it is economical in network devices connection. However, with the dramatic reduction of optical deployment cost, optical fiber cable has become one of the most popular mediums for both new cabling installation and upgrades, including backbone, horizontal, and even desktop applications. There are several advantages which make fiber cable a more enticing infrastructure solution than its copper counterpart. This passage will present five reasons for the choice in optical fiber cable instead of copper cable.

Bandwidth

Copper cable has very limited bandwidth that is perfect for voice signals transmission, since it is made of copper which will cause high loss at high frequencies. However, optical fiber cable, consisting of glass, provides more bandwidth than copper cable and has standardized performance more than 10Gbps (some special-designed fiber optic cable can support data rate of 40Gbps, or even 100Gbps). More bandwidth means optical cable can carry more information with greater fidelity than copper cable. For example, a cat6a cable can only support the maximum link length of up to 100 m at data rate of 10Gbps, while a multimode fiber optic cable can support the maximum link length of up to 10 km at the same data rate of 10Gbps.

Speed and Distance

Fiber optic cable transmission versus copper cable transmission can be boiled down to the speed of photons versus the speed of electrons. Copper cable uses electric waves to send signals, which makes it only suitable for short distance transmission, since the electric signals will start to break down when applied to higher speed and greater distance applications. However, the fiber optic signal is made of light, which will cause little signal loss during transmission, allowing data to move at higher speeds and greater distances. Therefore, Fiber optic cable does not have the 100-meter distance limitation like copper cable, and its distances can range from 550 meters to 40 km, depending on different cable types (single-mode fiber or multimode fiber), different data rates and different wavelengths. The following image shows different bandwidth and distance of fiber cable and copper cable.

Security

The data transmitted over the fiber are always safe. Eavesdropping on a LAN using copper cables only requires a sensitive antenna to pick up the energy radiated from the cable. Since fiber optic cable doesn’t transmit electricity, it won’t radiate energy and cannot be tapped by an antenna, while the copper cable using electricity is easy to be tapped which will cause the entire system to fail. The optical fiber does not produce EMI, so it cannot catch on fire. Besides, you will not have to worry about replacing fiber cables as frequently as copper cables. Because the fiber core is made of glass, the optical fiber won’t break as easily as copper based cable.

Immunity and Reliability

There are a number of factors that can cause outages when an organization is reliant on copper cable-based network, such as temperature fluctuations, severe weather conditions, and moisture. However, fiber cable is completely immune to these environmental factors that makes it extremely reliable in data transmission. You can use armored fiber cable in some harsh environment, and there is also bend water-proof fiber patch designed for weather exposure conditions. What’s more, fiber cable is also impervious to electrometric interference (EMI) and radio-frequency interference (RFI), crosstalk, impedance problems and so on. You can apply fiber cable next to industrial equipment without worry.

Cost

A few years ago, the overall price of fiber cables was 100% to 200% higher than copper cables. With the maturity of production technology, the cost for fiber cables, components, and hardware has steadily decreased. Fiber cable is certainly more expensive compared to copper cable when you are looking at it on a short term basis, but cheaper in the long term, since fiber cable costs less to maintain and needs less networking hardware compared to its copper counterpart.

Summary

With its wide bandwidth, high speed, long distance, great security and reliability, as well as low cost, fiber cable has already replaced the copper cable in many aspects of networking. As fiber optic connectivity improves, fiber construction will become more convenient. FS.COM provides a wide range of fiber optic cables for different applications. If you have related needs, please kindly visit FS.COM or contact sales@fs.com.

Fiber Optic Transceivers With CWDM Technology

CWDM (coarse wavelength division multiplexing) is the low-cost type of WDM technology, which is often used in metropolitan area network access networks. It is considered to be a flexible and economical solution to expand the existing network capacity without adding additional optical fibers. There are many devices deploying with CWDM technology used in telecommunication applications, like CWDM modules and CWDM Mux/Demux, to provide a cost-effective way for migrating to higher-rate infrastructures. This post will mainly introduce several fiber optic transceivers with CWDM technology.

Overview of CWDM Transceiver and Its Working Principle

CWDM transceiver is a hot-pluggable transceiver that combines with CWDM technology usually used to achieve connectivity between existing network equipment and CWDM Mux/Demux. This type of transceiver module can provide high-capacity bandwidth by carrying up to 16 channels on a single fiber in the spectrum grid from 1270 nm to 1610 nm with a 20 nm channel spacing, when used with CWDM Mux/Demux.

Similar to the working principle of prism, there is a multiplexer and a demultiplexer at the either end of the whole CWDM system. A multiplexer is at the transmitting end to combine several signals together, and a demultiplexer is at the receiving end to split the signals apart. The more detailed information can be see in the following image.

Several CWDM Transceiver Types

Actually, with the increasing need for CWDM technology in different applications, there are many types of fiber optic transceivers with CWDM technology, such as CWDM SFP, CWDM SFP+, CWDM XFP, CWDM X2, and CWDM XENPAK, etc. In the following part I will mainly introduce CWDM SFP, CWDM SFP+ and CWDM XFP.

CWDM SFP: CWDM SFP is hot-pluggable and transceiver component which is compliant with SFP MSA and IEEE 802.3 & ROHS. The transceiver uses a LC single-mode fiber to achieve data rates of 1G, 2G and 4G for the maximum link length of up to 200 km. You can connect the CWDM SFPs to CWDM passive optical system, add/drop multiplexer (OADM) modules or multiplexer and demultiplexer plug-in modules using single-mode fiber optic cables. Here is a Cisco CWDM-SFP-1270.

CWDM SFP+: CWDM SFP+ as shown below is based on the popular SFP form factor, which is an MSA standard build. It is designed for 10G Ethernet applications in data center, campus and metropolitan area access networks where require flexible and cost-effective systems. This type of CWDM module can reach a maximum speed of 11.25Gbps and is commonly used to support up to eight channels of 10G Ethernet over single-mode fiber at the wavelength including 1490 nm, 1510 nm, 1530 nm,1550 nm, 1570 nm, 1590 nm and 1610 nm.

CWDM XFP: CWDM XFP as shown in the image below, compatible with XFP MSA, is designed for single-mode fiber and operates at a nominal wavelength of CWDM technology, from 1270 nm to 1610 nm. CWDM XFP is mainly used for typical routers and switch line card applications.

Advantages of CWDM Transceiver

• Cost-saving—As we have mentioned above, CWDM module combining with CWDM technology can share a single fiber with several optical connections, thus expanding the bandwidth of fiber and allowing multiple applications to run over the same resources, which saves more cost than using other types of optical transceivers. Besides, due to the broader channel spacing in CWDM, cheaper uncooled lasers are used in CWDM modules, giving them another cost advantage.
• Increasing Network Capacity—By transmitting multiple data channels using separate optical wavelengths on the same optical fiber, CWDM modules can greatly increase network capacity. They reduce network equipment inventories, and eliminate the need to maintain extra units or devices with various fiber types for network repairs or upgrades. They can also enable the network to upgrade and to be in use over a longer time without replacing the whole network by providing interchangeable fiber connectors which can easily adapt to and modify any existing network.
• Low Power-consumption—Another advantage of CWDM module is low power-consumption. CWDM lasers without thermoelectric cooler and temperature control function, it is possible to significantly reduce the power consumption. For example a DWDM based module each laser is about 4 W power consumption, while the cooler CWDM module laser consumes only 0.5 W.

Summary

CWDM transceiver provides high speed and physical compactness that today’s networks require while delivering the deployment flexibility and inventory control that network administrators demand. FS.COM offers a wide range of CWDM modules, including the common used three types we have mentioned above, and the types we don’t discussed in detail, like CWDM X2, CWDM XENPAK, and CWDM GBIC. All of these modules are fully compatible with the original brand ones. You can come to FS.com for more detailed information.

Introduction to Three Cisco SFP Module Types

Although the 10 Gigabit Ethernet system has become the dominant deployment in telecommunication market, there are still many 1GbE infrastructures existing in today’s networks. SFP optical transceiver, as a critical component to support 1G data transmission, is also increasingly required in most Gigabit Ethernet networks. Many vendors, like Cisco, one of the most well-known and reliable company in telecommunication industry, have provided various types of SFP transceiver modules to the market. This post aims to introduce three common Cisco SFP module types for you references.

SFP Optical Transceiver Overview

SFP (small form factor pluggable) transceivers are hot-plugable and compact optical transceivers which provide instant fiber or copper connectivity for SONET, Gigabit Ethernet, Fibre Channel, and other communications standards. They are a cost-effective way to connect a single network device to a wide variety of fiber cable distances and types. With the existence of SFP module, network upgrades could be easier, since SFP is interchangeable fiber connectors that can adapt to any existing network. For example, by simply replacing the pluggable optical transceiver, a media converter that was originally used in a multimode network can be re-configured to operate over a CWDM network. SFP optics come in four versions: 1000Base-T, 1000Base-SX, 1000Base-LX, and 1000Base-ZX. The 1000Base-SX will work on multimode fiber for the link length of 550 m, while the 1000Base-LX and 1000Base-ZX work only on single-mode fiber for the maximum distance of 10 km and 80 km respectively, and the 1000Base-T is the RJ-45 version. The following image shows the structure of SFP module.

Three Common Cisco SFP Module Types

GLC-SX-MM SFP: GLC-SX-MM 1000Base-SX SFP is a duplex SFP transceiver used over multimode fiber at the wavelength of 850 nm for optical communications. It is compatible with IEEE 802.3z and could support the data rate of 1Gbps for the reach of 550 meters over 50/125 multimode fiber, and 220 meters over 62.5/125 multimode fiber. But since March 8th, 2013, there is no longer GLC-SX-MM SFP modules on sale in Cisco. It is replaced by the new model SFP transceiver module—GLC-SX-MMD SFP. However, for usage and cost considerations, many users still use the old model SFP, because GLC-SX-MMD is much more expensive, and except the additional DOM function, they work as the same when used in Cisco switch. These old Cisco compatible GLC-SX-MM SFPs can be still purchased in Fiberstore at very lower prices as shown in the following image.

GLC-LX-SM SFP: GLC-LH-SM 1000Base-LX-LH Ethernet transceiver is a LC duplex SFP transceiver used for optical networks. It operates at 1310 wavelength, rated for distances up to 10 km and a maximum bandwidth of 1Gbps. This type of SFP module is compliant with MSA (multisource agreement) and the IEEE 802.3z 1000Base-LX standard, which can both operate over single-mode fiber for the link spans of up to 10 km and up to 550 m on any multimode fibers. The following picture is Cisco GLC-LH-SM-15 Compatible 1000BASE-LXLH SFP in Fiberstore.

GLC-T SFP: GLC-T (as shown below) is a type of copper SFP module used over standard Cat5 unshielded twisted pair copper cabling of link length up to 100 m (328ft). It provides 1Gbps data transfer and offers full-duplex Gigabit Ethernet connectivity to high-end workstations and between wiring closets over existing copper network infrastructure. Cisco GLC-T SFP transceiver module can offer a flexible and simple method to be installed into SFP MSA compliant ports at any time with no interruption of the host equipment operation. It enables for seamless integration of fiber with copper LAN connections wherever SFP interface slots can be found.

Summary

We have mentioned three commonly used Cisco SFP modules in the previous text, and each module is applied in different applications. GLC-SX-MM SFP is used for multimode fiber based equipment, while GLC-LX-SM SFP is more suitable for single-mode fiber based infrastructure and GLC-T SFP is often deployed with copper cable, like Cat5 Ethernet cable. Besides these aspects, you should also take your budget into consideration. As we all know, Cisco brand SFP transceiver is expensive, but with the increasing popularity of third-party modules, we have a good alternative. Fiberstore provides a wide range of Cisco compatible SFP modules at affordable prices. If you have related needs, please visit FS.COM for more information.

A Brief Overview of 100G Transceivers and Cabling Solutions

Although 10G/40G has become the mainstream on telecommunication network market nowadays, service providers and enterprise data centers are still demanding higher data transmission speed to achieve higher level of performance and scalability, which explains why 100G Ethernet appeared on the scene. According to the statistics from market research company like IHS, 100G becomes a hit in the year of 2016. This post tends to give a brief overview of optical transceivers and cabling solutions for 100G Ethernet.

100G Ethernet Introduction

100 Gigabit Ethernet (100GbE) is the computer networking technology which was first defined by IEEE 802.3ba-2010 standard for transmitting Ethernet frames at rates of 100 gigabits per second. The 100G standards define numerous port types with different optical and electrical interfaces and different numbers of optical fiber strands per port. The mainly used 100G standards are showed in the following table.

100G Transceivers

Optical transceiver is considered to be a key component to ensure the flexibility and reliability of the whole system. The most commonly used 100G transceivers on the market are CFP, CFP2, CFP4 and QSFP28. The following part will introduce them in details.

CFP/CFP2/CFP4: The CFP (c form-factor pluggable) is a multi-source agreement (MSA) to produce a common form-factor for the transmission of high-speed digital signals. The “c” stands for the Latin letter C used to express the number 100 (centum), since the standard was primarily developed for 100 Gigabit Ethernet. The CFP transceiver can be used to support both single-mode fiber, multimode fiber and a variety of data rates, protocols, and link lengths. While the electrical connection of a CFP uses 10×10 Gbit/s lanes in each direction (RX, TX), the optical connection can support both 10×10 Gbit/s and 4×25 Gbit/s variants of 100Gbit/s interconnects. With the improvement in technology, higher-density and higher-performance CFP2 and CFP4 transceivers are needed. CFP2 and CFP4 has the similar electrical connection with the CFP, but they specify a form-factor of 1/2 and 1/4 respectively in size of the original specification. When you use these transceiver modules, you should note that they are not interchangeable, but they can be inter-operable at the optical interface with appropriate connectors. The image below shows CFP, CFP2 and CFP4 transceivers.

QSFP28: QSFP28 is a hot-pluggable, high-density transceiver available in single-mode and multimode versions to support data center, cloud networks, and high-performance computing networks applications. Just as the 40G QSFP+ is implemented with four 10Gbs lanes, the QSFP28 uses four 25 Gbs lanes for an aggregate data rate of 100Gbs. Typically, there are two versions of QSFP28 transceivers, 100GBase-SR4 QSFP28 for short distance data transmission and 100GBase-LR4 QSFP28 for long distance data transmission. The following picture shows these two types.

100G Cabling Solutions

100G Direct Cabling Solutions: There are various 100G direct cabling solutions available on the market. You can choose the appropriate one according to the data transmission distance that you require. For 100G short direct cabling, we can use 100GBase-SR4 QSFP28 and 100G QSFP28 to QSFP28 cables. As we all know, 100GBase-SR4 QSFP28 can support the length of up to 70 m and 100 m over OM3 and OM4 12 fiber multimode MTP cable respectively, and 100G QSFP28 to QSFP28 passive direct attach cable can support up to 5 m, while the 100G QSFP28 to QSFP28 active direct attach cable can support up to 10 m. For 100G long direct cabling, 100GBase-LR4 transceivers (including 100GBase-LR4 QSFP28, CFP, CFP2 and CFP4) are good choices. All of them can achieve the link length of up to 10 km on single-mode LC patch cables. Here shows a Cisco QSFP-100G-CU3M passive direct attach copper cable.

100G Breakout Cabling Solution: 100G QSFP28 to 4SFP28 direct attach copper cable (shown in the following picture) is the commonly used cable type for 100G breakout cabling applications. This cable provides connectivity between system units with SFP28 port on one side and four different SFP28 ports on the other side, which enables higher port bandwidth, density and configurability at a low cost and reduces power requirement in data centers.

Conclusion

People never stop chasing higher speed in every aspect of our daily life, so does in telecommunication networks. After the prevalence of 10G/40G, are you ready for 100G? Through the information that we have mentioned, hope you can get some basic knowledge to make good preparation for the coming of 100G.

OTDR – Making it Easier to Test Optical Fiber Cabling Faults

Communication networks never go slower, never get simpler, and never stay the same. Likewise, certification testing for fiber-optic cabling has also changed. Various test equipment and enhanced testing regiments are manufactured by many vendors to ensure that cabling can support the new demands placed on networks. Among them, OTDR (shown in the following picture) is a new generation of fiber test equipment, which can make it easier to ensure consistent quality in an optical fiber. I’d like to introduce this new testing tool for you in the following part.

What Is OTDR?

OTDR, also called as optical time domain reflectometer, is an optoelectronic instrument which is basically used to identify and analyze reflective and non-reflective events that cause disturbance in an optical fiber link. OTDR are most effective when testing long cables (more than approximately 250 meters or 800 feet) or cable plants with splices. The data that OTDR produces is typically used to create a picture called as a trace or signature, which can be used for troubleshooting, since it shows where breaks are in fiber, when the trace or signature is compared to installation document. Using OTDR, you can easily confirm the quality of fibers and find where network trouble arises. There are various of OTDR available with different fiber types (like single-mode fiber) and wavelengths (such as 1310 nm, 1550 nm and 1625 nm). The image below shows the working principle of OTDR.

Working Principle of OTDR

OTDR uses the effect of rayleigh scattering and fresnel reflection to measure the characteristics of an optical fiber. In essence, it takes a snapshot of the fiber’s optical characteristics (the trace of length vs returned signal level) by sending high-powered pulse into one end of the fiber and measuring the light scattered back toward the instrument.

As we mentioned above, the trace, which can be analyzed on the spot, printed out immediately for documentation of the system, or saved to a computer for later analysis and comparison, is referred by trained operator to locate the end of the fiber, the location and loss of splices, and the overall loss of the fiber.

What can OTDR Be Used for?

OTDR is widely used in many phases of a fiber system’s life, from the construction, to maintenance, to fault locating and restoration. The following part lists some aspects that it can be utilized:

• Locating fiber cable breaks or cuts. OTDR can be used to predict the distance (in meters from the source) where the optical fiber cable has been disconnected.
• Measuring reflectance or optical return loss (ORL) of connectors and mechanical splices for CATV, SONET, and other analog or high-speed digital systems where reflections must be kept down.
• Identifying dissimilar and mismatched fibers (for example, 50 micron fiber and 62.5 micron fiber) that are connected together affecting the intensity of the light signal.
• Spotting usage of fiber patch cords with a different/incorrect core size that affects signal strength.
• Detecting the gradual or sudden degradation of fiber by making comparisons to previously-documented fiber tests.

Using Tips for OTDR Tester

When using an OTDR, there are a few tips that will make testing easier and more understandable:

• Always using a long launch cable, which allows the OTDR to settle down after the initial pulse and provides a reference cable for testing the first connector on the cable.
• Always start with the OTDR set for the shortest pulse width for best resolution and a range at least twice the length of the cable you are testing.
• Make initial trace and see how you need to change the parameters to get better results.

Conclusion

OTDR is an easier solution to test or identify faults in an installed fiber optic cable network as well as certify new fiber optic cable installation. This text has provided you with some basic information about OTDR tester and tell you several helpful tips for using OTDR tester. Besides OTDR that offered in fiberstore, there are various other types of optical testers, such as VSL (visual fault locator), ADSL tester, optical power meter, and so on. Each tester has unique functions and is used in different applications. If you want to know more information, please visit FS.COM.