The Application of Fiber to the Desk (FTTD)

As communication technology develops rapidly, the demand for higher bandwidth is increasing. To solve this problem, optical cable is widely used as the backbone of communications network cabling, especially in big data center. In recent years, projects like FTTH (Fiber to the Home) and FTTB (Fiber to the Building) are carried out to provide better services for customers. To future capitalize on the benefits of optical cable, Fiber to the Desk (FTTD) is recommended for enterprises, financial institutions and federal agencies, which need high security and high data transmission speed. This article will guide you to have a closer look at application of FTTD.


FTTD refers to the extension of the fiber optic infrastructure directly to user locations, just as the following figure show, optical cables are directly connected to desktops, laptops, or other communications equipment. FTTD can be used for virtual networks using thin clients and LAN networks with extended distances to workstations. It can satisfy the requirement for increasing bandwidth availability, moving large amounts of data at high transmission rates. In addition, it is able to bring service to locations where power is limited or unavailable as well as provide a more secure connection for organizations who are concerned about tapping or other security vulnerabilities.



We know that RI45 Ethernet cable can also be used as transmission media. What makes optical cable superior to RJ45 Ethernet cable? This part will show you the advantages of using optical cable for FTTD project.


Optical cable is immune to electromagnetic interference (EMI) and radio-frequency interference (RFI), so it is more difficult for hackers to tap on optical cable. Besides, optical cable uses light that is completely shielded, so hackers would have to physically splice into the line, which is difficult to do and easily detected. While RJ45 Ethernet cable emits electromagnetic signals which allows hackers to read data from nearby without physically touching the lines. In contrast, optical cable is a more secure option for applications concerned with data security.

Bandwidth And Distance

Optical cable is able to support higher data rates than any other cable type, with capacity to transmit up to 100 Gbit/s. As demand for higher bandwidth is ever-growing, optical cable has the absolute advantage. What’s more, connected with appropriate optics, the transmission distance of optical cable can reach dozen kilometers. Although higher grades of RJ45 Ethernet cables can transmit 10G data signals, they will only be able to do so over very short distances. Therefore, optical cable is the best choice for transporting higher speed and higher bandwidth signals over longer distances.

Lower Overall Cost

Optical cable used to be more expensive than RJ45 Ethernet cable. As demand has increased, manufacturing costs have dropped. Also, if properly designed, the FTTD project could be affordable. Apart from this, optical cable can ensure your network cabling can keep up with the growth in network traffic over time and upgrade your network to higher bandwidth in the future without recabling. Considering the cost of cabling, this can be a huge advantage. Though the initial cost of fiber equipment may be slightly higher than copper, the benefits realized can save organizations significant cost in the long term.

optical cable vs. RJ45 Ethernet cable

Optical cable Vs. RJ45 Ethernet cable


FTTD is a high-bandwidth solution that expands the traditional fiber backbone system by running fiber directly to desktops. FTTD is a horizontal wiring option that pushes the available bandwidth beyond 10G. It is an intriguing, underestimated and overlooked way to create a beneficial system that is expandable and performance-driven. The optical cable, fiber optic wall plate, PoE media converter and some other fiber optics used in FTTD are available in FS.COM. For more details, you can visit our site.

Connectivity Solutions for Parallel to Duplex Optics

Since we have discussed connectivity solutions for two duplex optics or two parallel optics in the last post (see previous post: Connectivity Solutions for Duplex and Parallel Optics), the connectivity solutions for parallel to duplex optics will be discussed in this article, including 8-fiber to 2-fiber, and 20-fiber to 2-fiber.

Parallel to Duplex Direct Connectivity

When directly connecting one 8-fiber transceiver to four duplex transceivers, an 8-fiber MTP to duplex LC harness cable is needed. The harness will have four LC duplex connectors and the fibers will be paired in a specific way, assuring the proper polarity is maintained. This solution is suggested only for short distance within a given row or in the same rack/cabinet.

8-fiber to 2-fiber direct connectivity

Figure 1: 8-fiber to 2-fiber direct connectivity

Parallel to Duplex Interconnect

This is an 8-fiber to 2-fiber interconnect. The solution in figure 2 allows for patching on both ends of the fiber optic link. The devices used in this link are recorded in the table below figure 2.

8-fiber to 2-fiber interconnect

Figure 2: 8-fiber to 2-fiber interconnect

Item Description
1 8 fibers MTP trunk cable (not pinned to pinned)
2 96 fibers MTP adapter panel (8 ports)
3 8 fibers MTP trunk cable (not pinned)
4 MTP-8 to duplex LC breakout module (pinned)
5 LC to LC duplex patch cable (SMF/MMF)

Figure 3 is also an interconnect for 8-fiber parallel QSFP+ to 2-fiber SFP+. This solution is an easy way for migration from 2-fiber to 8-fiber, but it has disadvantage that the flexibility of the SFP+ end is lacked because the SFP+ ports have to be located on the same chassis.

8-fiber to 2-fiber interconnect

Figure 3: 8-fiber to 2-fiber interconnect

Item Description
1 8 fibers MTP trunk cable (not pinned to pinned)
2 96 fibers MTP adapter panel (8 ports)
3 8 fibers MTP trunk cable (not pinned)
4 8 fibers MTP (pinned) to duplex 4 x LC harness cable

Figure 4 shows how to take a 20-fiber CFP and break it out to ten 2-fiber SFP+ transceivers. The breakout modules divide the twenty fibers into three groups, and ten LC duplex cables are used to accomplish the connectivity to SFP+ modules.

20-fiber to 2-fiber interconnect

Figure 4: 20-fiber to 2-fiber interconnect

Item Description
1 1×3 MTP breakout harness cable(24-fiber MTP to three 8-fiber MTP) (not pinned)
2 MTP-8 to duplex LC breakout module (pinned)
3 LC to LC duplex cable (SMF/MMF)
Parallel to Duplex Cross-Connect

There are two cross-connect solutions for 8-fiber parallel to 2-fiber duplex. The main difference for figure 5 and 6 is on the QSFP+ side. The second cross-connect is better for a greater distance between distribution areas where the trunk cables need to be protected from damage in a tray.

8-fiber to 2-fiber cross-connect (1)

Figure 5: 8-fiber to 2-fiber cross-connect (1)

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

8-fiber to 2-fiber cross-connect (2)

Figure 6: 8-fiber to 2-fiber cross-connect (2)

Item Description
1 8 fibers MTP trunk cable (not pinned to pinned)
2 96 fibers MTP adapter panel (8 ports)
3 8 fiber MTP trunk cable (not pinned)
4 MTP-8 to duplex LC breakout module (pinned)
5 LC to LC duplex cable (SMF/MMF)

These solutions are simple explanations to duplex and parallel optical links. It seems that the difference between each solution is not that significant in plain drawing, but actually the requirements for components are essential to an efficient fiber optic network infrastructure in different situations. Whether it is a narrow-space data center or a long-haul distribution network that will mostly determine the cabling structure and the products used.

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)

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.

Have You Chosen the Right Power Cord?

Different cables have particular applications. Some are used for data transmission like fiber optic cable or copper cable, and some are used for the transmission of electrical power. Power cord is the assembly widely used as the connection between main electricity supply and the device through a wall socket or extension cord. Power cord is adopted in almost every where when the alternating current power is required. However, have you chosen the right type of power cord for your device? From this article, you may find the answers.

power cord

Overview of Power Cord

A power cord set usually has connectors molded to the cord at each end, thus both ends can detach from the power supply and device. Specifically, power cord assembly consists of three major parts. First is the cable plug, and it is also a male connector used for inserting into the AC outlet to provide power. Then is the receptacle on the other end. Receptacle part is also known as the female connector attached to equipment. Cord is the main section that contains the insulated wires with different lengths and thicknesses.

power cord structure

Common Types of Power Cord

According to different plug and receptacle styles, power cords have different standards. In North America, NEMA power cords and IEC 60320 power cords are the common types with the standards set by NEMA (National Electrical Manufacturers Association) or IEC (International Electrotechnical Commission). Let’s have a look at their differences.

NEMA Power Cord

NEMA power cords have two series of NEMA 5 and NEMA 6. NEMA 5 series is the type widely found in the United States. It has three-wire circuits (hot, neutral, and ground) and is rated to carry a maximum of 125 volts although usually carries about 110 volts and are referred to as “110 circuits”. NEMA 6 series connectors are used for providing heavy duty power to a device. These are typically 208 volt or 240 volt circuits and often referred to as “220 circuits”.

NEMA Power Cord

IEC 60320 Power Cord

The ends of IEC 60320 power cord are on the opposite side of the cord from the power plug. To make it an international standard, the equipment manufacturers need to put one kind of receptacle on their equipment and then manufacture the various country-specific cords when needed. The IEC 60320 C13/C14 connector type is seen on most personal computers and monitors. C19/C20 connector type is used for devices like servers and UPS (Uninterruptible Power Supply) systems.

IEC 60320 power cord

How to Organize Power Cords?

Just like other types of cables, too many power cords can also be easily mixed up during work. Fortunately, there is a simple way to organize the power cords. Instead of labeling all the power cords, you can buy the colored cords for identification. For example, red power cords can be used for important device, and green or blue cords can be used for constantly rearranged equipment. Color coding the system is definitely a more efficient way for cable management.

colorful power cord


The standardization of power cords provides great help for the convenient connectivity when powering different kinds of devices. There is usually a long list of power options for the switch or server. You might be confused when all the components are using the acronyms you don’t know. Therefore, understanding the standards can make the selection of power cords much easier.

How to Choose Single-mode Fiber?

The common sense is that fiber optic patch cable can be divided into singlemode and multi-mode types. As we all know, multimode fiber is often divided into OM1, OM2, OM3 and OM4. So what is about the multi-mode fiber? Actually, the division of the multi-fiber is kind of complex. There are two primary sources of specification of single-mode optical fiber. One is the ITU-T G.65x series, and the other is IEC 60793-2-50 (published as BS EN 60793-2-50). This article will only focus on the part of ITU-T G.65x that defines 19 different single-mode optical fiber specifications. You can see the different types and the evolution process of them in the below table, which can be the miniature of the evolution of transmission system technology from the earliest installation of single-mode optical fiber through to the present day.

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 ITU-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

After you have a basic knowledge of this, next we will discuss how to choose the right one for your project in terms of performance, cost, reliability and safety. And in order to make this question easier to answer, we will get down to the aspect of the differences between the specifications of the G.65x series of single-mode optical fiber families.


The ITU-T G.652 standard fiber is the most commonly deployed one. 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 1310-nm band. They can also operate in the 1550-nm 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 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 unacceptabdle crosstalk and interference between channels.


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 1550-nm 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 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 1550-nm 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.


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 allow the easier deployment of CWDM in metropolitan areas, and increase the capacity of fiber in DWDM systems.


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.


From the above analysis, we can learn that different kinds of single-mode fiber has different applications. Since G.657 is compatible with the G.652, some planners and installers are usually likely to come across them. In fact, G657 has a larger bend radius than G.652, which is especially suitable for FTTH applications. And due to problems of G.643 being used in WDM system, it is now rarely deployed, being superseded by G.655. G.654 is mainly used in subsea application. After reading this article, I hope you have a clear understanding about these single-mode fibers, which may help you make the right decision.