Light is a type of electromagnetic wave. It consists of oscillating electrical fields, denoted by E, and magnetic fields, denoted by B. Its properties can be described by studying its electrical field E, although we could just as well describe light and its effects in terms of the magnetic field.

Light waves can vibrate in many directions. Those that are vibrating in one direction – in a single plane such as up and down – are called polarized light. Those that are vibrating in more than one direction – in more than one plane such as both up/down and left/right – are called unpolarized light.


The most common method of achieving single polarization is using a polarization filter. Polarization filters are made of special materials that are capable of blocking one of the two planes of vibration of an electromagnetic wave.

Polarization filter serves as a device which filters out one-half of the vibrations upon transmission of the light through the filter. When unpolarized light is transmitted through a polarization filter, it emerges with one-half the intensity and with vibrations in a single plane; it emerges as polarized light.


Polarization maintaining fiber (PM Fiber) is a special type of single mode fiber. Normal single mode fibers are capable  of carrying randomly polarized light. However, PM fiber is designed to propagate only one polarization of the input light.

In polarization maintaining fiber, the polarization of linearly-polarized light waves launched into the fiber is maintained during propagation, with little or no cross-coupling of optical power between the polarization modes. This polarization maintaining feature is extremely important for some fiber optic components such as external modulators that require a polarized light input.

This characteristic is achieved during the manufacturing process by inducing stresses in the material itself. There are two categories of polarization maintaining fiber (PMF) available, linear polarization maintaining fiber (LPMF) and circular polarization maintaining fiber (CPMF).


 These fibers contain a feature not seen in other fiber types. Besides the fiber core, there are stress rods in the fibers. The stress rods are two circles in the Panda PM fiber, a elliptical clad in elliptical-clad PM fiber and two bow-ties in the Bow-Tie type PM fiber.

As their name implies, these stress rods create stress in the core of the fiber such that the transmission of only one polarization plane of light is favored.

When PM fibers are terminated with fiber connectors, it is very important that the stress rods line up with the connector, usually in line with the connector key.

PM fiber also requires a great deal of care when it is spliced. Not only the X,Y and Z alignment have to be perfect when the fiber is melted together, the rotational alignment must also be perfect so that the stress rods align exactly.

Another requirement is that the launch conditions at the optical fiber end face must be consistent with the direction of the transverse major axis of the fiber cross section.


1.PM optical fibers are used in special applications, such as fiber optic sensing, interferometry and slab dielectric waveguides

2.PM fibers are expected to be used in coherent optical transmission systems or long distance bidirectional optical transmission systems

3.They may also be used in transmission applications where the polarization plane of the optical signal is important, such as transmission lines for optical sensors and coupling for optical electrical integrated circuits

4.PM fibers are used in lithium niobate modulators, Raman amplifiers, and other polarization sensitive systems to maintain the polarization of the incoming light and keep cross-coupling between polarization modes at a minimum.


 Fiber optic attenuators are used in applications where the optical signal is too strong and needs to be reduced.

For example, in a multi-wavelength fiber optic system, you need to equalize the optical channel strength so that all the channels have similar power levels. This means to reduce stronger channels’ powers to match lower power channels. 

Another example is when the received optical power is so strong that it saturates the receiver, you need an attenuator to reduce the power so the receiver can detect the signal correctly.

This picture shows an example of a fixed optical attenuator. The attenuation level is fixed at 5 dB, which means it reduces the optical power by 5dB. This attenuator has a short piece of fiber with metal ion doping that provides the specified attenuation.

There are many different mechanisms to reduce the optical power, this picture shows another mechanism used in one type of variable attenuator. Here variable means the attenuation level can be adjusted, for example, it could be from 1 dB up to 20dB.

In this example, the light from the input fiber is expanded into a larger beam by the first collimating lens, then a blocking device, which could be a neutral density filter, is inserted into the light path to partially block the light, so only part of the light can pass through. Then the second collimating lens is used to focus the light back into the output fiber. When you move the blocking device inward or outward, you get different attenuation levels.

Fiber optic attenuators are usually used in two scenarios.

The first case is in fiber optic power level testing. Attenuators are used to temporarily add a calibrated amount of signal loss in order to test the power level margins in a fiber optic communication system.

In the second case, attenuators are permanently installed in a fiber optic communication link to properly match transmitter and receiver optical signal levels.

Optical attenuators are typically classified as fixed or variable attenuators.

Fixed attenuators have a fixed optical power reduction number, such as 1dB, 5dB, 10dB, etc.

Variable attenuators’ attenuation level can be adjusted, such as from 0.5 dB to 20dB, or even 50dB. Some variable attenuators have very fine resolution, such as 0.1dB, or even 0.01dB.

This slide shows many different optical attenuator designs.

The female to female fixed attenuators work like a regular adapter. But instead of minimizing insertion loss, it purposely adds some attenuation.

The female to female variable attenuators are adjustable by turning a nut in the middle. The nut adjusts the air gap in the middle to achieve different attenuation levels.

The male to female fixed attenuators work as fiber connectors, you can just plug in your existing fiber connector to its female side.

The in-line patch cable type variable attenuators work as regular patch cables, but your can adjust its attenuation level by turning the screw.

For precise testing purposes, engineers have also designed instrument type variable attenuators. These instrument type attenuators have high attenuation ranges, such as from 0.5 dB to 70dB. They also have very fine resolution, such as 0.01dB. This is critical for accurate testing.

Introduction of Optical Fiber Couplers and How Do They Work?

 What are optical fiber couplers?

A fiber optic coupler can be defined as an optical component used with one or more input fibers and several output fibers in fiber optic systems. A coupler essentially puts two or more cores of fibers together to connect. The simple coupler is the fused fiber 2×2 coupler.

Couplers are used as multiplexers that are resistant to certain wavelengths. A fiber output depends on the wavelength of light and the frequency of polarization. The fiber refractive index also plays a significant role in the performance. Let’s checkout how do optic couplers work to understand this better.

How do fiber optic couplers work?

Either fiber optic couplers separate optical signals into multiple paths or combine multiple signals in one direction. Optical signals are more complicated than electrical signals, making it more difficult to design optical couplers than their electrical copy. Unlike electrical currents, the optical signal consists of a stream of signal carriers, in this case photons.

The optical signal, however, does not stream to the ground through the receiver. Alternatively, a sensor absorbs the signal stream at the transmitter. Many receivers, connected in a row, would not receive a signal after the first receiver absorbs the whole signal.

Multiple parallel optical output ports therefore need to split the signal between the ports, increasing their magnitude. A coupler is defined by the number of input and output ports expressed as a N x M configuration.  The letter N is the number of input fibers, and the number of output fibers is expressed by M. In any configuration, fused couplers can be made, but they typically use multiples of two (2x 2, 4x 4, 8x 8, etc.).

We always use digital couplers: like a telephone coupler that allows you to connect a telephone and a fax machine to the same telephone line. Or a CATV coupler that allows you to connect multiple TV sets from Comcast to a single cable. Essentially, you can purchase these couplers online at Connect Zone. Optical couplers have the same features as digital couplers: they distribute the signal to different (devices) points.

Fiber optic couplers are of two kinds – active and passive. The distinction between active and passive couplers is that without optical-to-electrical conversion, a passive coupler redistributes the optical signal. Active couplers are electronic devices that electrically separate and blend the signal and use input and output fiber optic detectors and sources.

Electronic couplers are easy to make as long as you have physical contact between conductors, electrical current flows. But optical signal is a completely different field. The tiny optical fiber cores need to be precisely spaced (9um for single mode and 50um or 62.5um for multimode fibers), so when you break the signal, there will not be a huge power loss.

ConnectZone is a leading cable company for over last 11 years providing quality network cable such as ethernet patch cable, network patch cable, fibre optic cable and more for the computer, storage and data network space. We also have expertise in custom networking cable solutions with exceptionally fast turnaround times. Shop for cables online at the most affordable rate!

Types of Fiber Optic Coupler

Fiber Optic Couplers are broadly classified into two, the active or passive devices. For the operation of active fiber coupler an external power source is required, conversely no power is needed when it comes to operate the passive fiber optic couplers.

Fiber Optic Couplers can be of different types for instance X couplers, PM Fiber Couplers, combiners, stars, splitters and trees etc. Let’s discuss the function of each of the type of the Fiber Optic Couplers:

Combiners: This type of Fiber Optic Coupler combines two signals and yields single output.

Splitters: These supply multiple (two) outputs by using the single optical signal. The splitters can be categorized into T couplers and Y couplers, with the former having an irregular power distribution and latter with equal power allocation.

Tree Couplers: The Tree couplers execute both the functions of combiners as well as splitters in just one device. This categorization is typically based upon the number of inputs and outputs ports. These are either single input with a multi-output or multi-input with a single output.

PM Coupler: This stands for Polarization Maintaining Fiber Coupler. It is a device which either coalesces the luminosity signals from two PM fibers into a one PM fiber, or splits the light rays from the input PM fiber into multiple output PM fibers. Its applications include PM fiber interferometers, signal monitoring in its systems, and also power sharing in polarization sensitive systems etc.

Star Coupler: The role of star coupler is to distribute power from the inputs to the outputs.

Benefits of Fiber Optical Couplers

There are several benefits of using fiber optic couplers. Such as:

Low excess loss,

High reliability,

High stability,

Dual operating window,

Low polarization dependent loss,

High directivity and Stumpy insertion loss.

The listed benefits of Fiber Optical Couplers make them ideal for many applications for instance community antenna networks, optical communication systems and fiber-to-home technology etc.

The right way to Choose Fiber Optical Splitter

How to Choose Fiber Optical Splitter

Fiber optic splitters play an increasingly significant role in many of today’s optical network topologies. They provide capabilities that help users maximize the functionality of optical network circuits from FTTx systems to traditional optical networks. And usually they are placed in the central office or in one of the distribution points (outdoor or indoor).

What Is Fiber Optic Splitter?

fiber optic splitter is a passive optical device that can split or separate an incident light beam into two or more light beams. These beams may or may not have the same optical power as the original beam, based on the configuration of the splitter. By means of construction, the outputs of an optical splitter can have varying degrees of throughput, which is highly beneficial when designing optical networks, whether the optical splitter is used for network monitoring or for a loss budget in passive optical network (PON) architecture. Generally, there are two types of fiber optic splitters, which are FBT splitters and PLC splitters.

FBT Splitter

FBT splitter is one of the most common splitters, which is widely accepted and used in passive networks. FBT splitter is designed for power splitting and tapping in telecommunication equipment, CATV network, and test equipment.

PLC Splitter

PLC splitter is a hot research at home and abroad today, with a good prospect of application, which is used to distribute or combine optical signals. It is based on planar light wave circuit technology and provides a low cost light distribution solution with small form factor and high reliability.

Applications for PLC Splitter

Bare Fiber PLC Splitter

Bare fiber PLC splitter has no connector at the bare fiber ends. It can be spliced with other optical fibers in the pigtail cassette, test instrument and WDM system, which minimizes the space occupation. It is commonly used for FTTH, PON, LAN, CATV, test equipment and other applications.

Blockless PLC Splitter

Likewise, blockless PLC splitter has a similar appearance as bare PLC splitter. But it has a more compact stainless tube package which provides stronger fiber protection, and its fiber ends are all terminated with fiber optic connectors. Connectors are commonly available with SC, LC, FC and ST types. Thus, there is no need for fiber splicing during installation. Blockless PLC splitter is mainly used for different connections over distribution boxes or network cabinets.

ABS PLC Splitter

ABS PLC splitter has a plastic ABS box to protect the PLC splitter to adapt to different installation environments and requirements. Common splitter modules are 1×4, 1×8, 1×16, 1×32, 1×64, 2×4, 2×8, 2×16, 2×32. It is widely used with outdoor fiber distribution box for PON, FTTH, FTTX, PON, GOPN networks.

Fanout PLC Splitter

PLC splitter with fan-out is mainly used for 0.9mm optical fiber where the ribbon fiber can convert to 0.9mm optical fiber through fan-out. 1×2, 1×4, 1×8, 1×16, 1×32, 1×64, 2×2, 2×4, 2×8, 2×16, 2×32, 2×64 fanout types are all available with PLC splitters. Fiber adapters can also be used for the input and output ends of this kind of splitters to directly meet the demand on smaller size of splitters.

Tray Type PLC Splitter

Tray type PLC splitter can be regarded the fiber enclosure which contains PLC fiber splitter inside a enclosure. It is often directly installed in optical fiber distribution box or optical distribution frame. FC, SC, ST & LC connectors are selective for termination. Tray type PLC splitter is an ideal solution for splitting at the places that are near OLT or ONU.

Rack-mount PLC Splitter

Rack-mount PLC splitter can be used for both indoor and outdoor applications in FTTx projects, CATV or data communication centers. It uses the 19-inch rack unit standard to contain the PLC splitter inside a rack unit.

LGX PLC Splitter

LGX PLC splitter or LGX box PLC splitter has a strong metal box to house the PLC splitters. It can be used alone or be easily installed in standard fiber patch panel or fiber enclosure. The standard LGX mental box housing provides a plug-and-play method for integration in the network, which eliminates any risk during installation. No filed splicing or skilled personnel is required during deployment.

Mini Plug-in Type PLC Splitter

Similar to the LGX PLC splitter, mini plug-in PLC type splitter is its small version with a compact design. It is usually installed in the wall mount FTTH box for fiber optic signal distribution. Using the mini plug-in PLC type splitter saves time and space but still provides reliable protection for the fiber optic splitter.

Brief introduction of Pre-Terminated Fiber Cables

 Fiber optic cables are critical to various industries and applications across the world. Unlike traditional copper cables, they are capable of transmitting large volumes of data at high speed. Additionally, they are light and flexible, making them easier to install, maintain, and repair, which has led to them being the go-to option for countless data transmission applications.

Fiber optic cables need to be terminated before they are installed. Termination refers to the process of adding a device to the end(s) of the cable that enables it to be connected to other cables and devices. While the process can be performed in the field, pre-terminated cables are terminated by the manufacturer before shipment and can improve installation efficiency and/or reduce installation costs.

How Are Fiber Cables Terminated?

The fiber optic cable termination process requires a variety of tools and supplies. It involves exposing the fiber elements and attaching them together. The connections formed can be temporary or permanent. Temporary connections use connector components, which are available in many designs to suit different applications. Permanent connections involve splicing, a process in which the bare fibers are connected directly.

Pre-Terminated Fiber Cable vs. Field-Terminated Fiber Cable

As indicated above, fiber cables can be field-terminated or pre-terminated. Field-terminated cables are terminated at the installation site. Pre-terminated cables are terminated at the manufacturing facility.

When Should I Use Pre-Terminated Fiber Optic Assemblies?

Pre-terminated fiber optic cables offer a variety of advantages over field-terminated fiber optic cables. Since they arrive on-site ready to use (i.e., they do not need to be prepared or tested), they are much quicker and easier to install. As a result, they can lead to lower labor costs and a smaller risk of installation error. If you’re looking to reduce project costs, shorten installation timelines, and/or decrease termination issues, pre-terminated fiber optic cables are the perfect solution.

When Should I Not Use Pre-Terminated Fiber Optic Assemblies?

While pre-terminated fiber optic cables are suitable for many applications, they are not suitable for every application. Since they are precut before they arrive on-site, they may not be as accurate or precise in length as field-terminated fiber optic cables. If high accuracy and precision are critical for an application, it may be better to use field-terminated cables to reduce the risk of measurement miscalculation.

Considerations for Pre-Terminated Fiber Optic Cables

There are many design options for pre-terminated fiber optic cable assemblies. Additionally, they are a variety of tools available to facilitate their installation.

Pre-Terminated Fiber Optic Cable Connectors

Fiber cables can be pre-terminated with a range of connector types. New types are regularly hitting the market while existing ones consistently receive improvements. The connector types available at Opticonx include:





We continuously work with connector manufacturers to ensure we remain up to date on the latest advancements in connector technologies.

Pull Eye Kits

While pre-terminated fiber cables are easier to use than field-terminated fiber cables, they still carry a risk of being strained during the installation process. The PEK series pulling eye kits from Opticonx are designed to protect pre-terminated cables while they are installed in conduits, ducts, or risers. The kits ensure terminations do not experience any stress or strain during installation.

Which Fiber Patch Cable Should I Choose for My Optical Transceiver?

 SFP fiber cable and fiber optic transceiver have become more and more important in fiber optic data transmission, especially in data transmission between the switches and equipment. But with so many different kinds of SFP fiber cables available in the market, which one is suitable for may optical transceiers? This article may on this issue to provide some solutions. Before starting this topic, it is necessary for us to review the basic knowledge of the fiber optic transceiver and fiber optic cable.

Fiber Optic Transceiver Overview

Fiber Optic Transceiver is a self-contained component that can both transmit and receive. Usually, it is inserted in devices such as switches, routers or network interface cards which provide one or more transceiver module slot. There are many optical transceivers types, such as SFP+ transceiver, X2 transceiver, XENPAK transceiver, XFP transceiver, SFP (Mini GBIC) transceiver, GBIC transceiver and so on.

Fiber Optic Patch Cable Overview

Fiber optic patch cable, also known as fiber jumper or fiber optic patch cord. It is composed of a fiber optic cable terminated with different connectors on the ends. Fiber optic patch cables are used in two major application areas: computer work station to outlet and patch panels or optical cross connect distribution center. According to fiber cable mode, cable structure or connector types etc., fiber patch cable can be divided into different types.

1.Single-mode and Multimode SFP fiber Cable

According cable mode, patch cables can be divided into single-mode and multimode fiber patch cable. The word mode means the transmitting mode of the fiber optic light in the fiber optic cable core. Single-mode patch cables are with 9/125 fiber glass and are yellow jacket color, while multimode patch cables are with OM1 62.5/125 or OM2 50/125 fiber glass and are orange color. In addition, there is 10G OM3 and OM4 multimode patch cables which cable jacket are usually aqua.

2.Simplex and Duplex SFP fiber Cable

Simplex fiber patch cable is consist of single fiber core, while duplex fiber patch cable is consist of two fiber cores and can be either singlemode or multimode. Additionally, there is also ribbon fan-out cable assembly (ie. one end is ribbon fiber with multi fibers and one ribbon fiber connector such as MTP connector (12 fibers), the other end is multi simplex fiber cables with connectors such as ST, SC, LC, etc.).

3.LC, SC, ST, FC, MT-RJ, E2000, MU and MPO/MTP Patch Cable

Fiber optic patch cable can be also classified by the types of fiber optic connector. For example, LC fiber optic patch cable is named as it is with LC connector. Similarly, there are SC, ST, FC, MT-RJ, E2000, MU and MPO/MTP fiber optic patch cables. What’s more, there are PC, UPC, APC type fiber patch cords, which are differentiated from the polish of fiber connectors.

Which SFP fiber Cable Should I Choose for My Fiber Optic Transceivers?

Now, I will take the Cisco fiber optic transceiver as an example to discuss this topic. For example, we need to choose a right patch cable to connect Cisco fiber optic transceiver SFP-10G-SR and X2-10GB-SR. Which patch cable to use? According to “Cisco 10-Gigabit Ethernet Transceiver Modules Compatibility Matrix”, we may know that SFP-10G-SR is the 10GBASE-SR SFP+ transceiver module for MMF, 850-nm wavelength, LC duplex connector. And X2-10GB-SR is the 10GBASE-SR X2 transceiver module for MMF, 850-nm wavelength, SC duplex connector. Obviously, this two knids of optica trancseivers are both for MMF, so we should choose a multimode patch cable. Besides, we know X2-10GB-SR is designed for SC duplex connector and the SFP-10G-SR is designed for duplex LC connector, so we should use a patch cable with SC-LC duplex connector.

The Most Common Used SFP fiber Cable Selection

In the way mentioned above, you could choose right fiber patch cable for your other transceiver modules. Keep in mind that if your transceiver modules are not Cisco’s, you need to ask your brand supplier to get the corresponding compatibility matrix. In fact, in terms of a same kind of optical transceiver, different supplier may provide the transceiver with different specifications. Here I may list the most common used patch cables selection. Hope to give you smoe reference.

For more info please visit:

%d bloggers like this: