Getting to Know Fiber Collimator

Passive optical components are widely used to ensure higher performance of optical networks. There are many kinds of passive optical devices deployed for different applications. Fiber collimator is an important type used for collimating optical light. In this article, we will get to know the basic knowledge of fiber collimator.

What Is Collimated Light?

Before getting to know fiber collimator, we should first understand the meaning of collimated light. Collimated light is the light whose rays are parallel, and therefore will spread minimally as it propagates. A perfectly collimated beam, with no divergence, would not disperse with distance and is sometimes said to be focused at infinity. Hence, a collimated light can travel along the right path to decrease fiber optic loss. However, in actual practice, optical lights may not always transfer in a right direction between different parts, such as from laser diode to fiber, from fiber to planar waveguide, or from micro-optical crystal to fiber, etc. In order to solve the problem, fiber collimator plays an important role in adjusting the light into the desired direction to enable the high performance of fiber optic transmission.


Introduction to Fiber Collimator

A fiber collimator is a device that narrows a beam of particles or waves. It can either cause the directions of light to become more aligned in a specific direction, or cause the spatial cross section of the beam to become smaller. Usually, fiber collimator is required to naturally transform diverging lights from an optical fiber to a parallel beam of light. It consists a single-mode or multimode fiber pigtail and a collimating lens. Collimator can also be used to calibrate other optical devices to check if all elements are aligned on the optical axis.


How Does It Work?

When placing the fiber end on the collimator lens, the light will be aligned to a parallel direction. Then through a slight adjustment of fiber end position, the working distance is obtained. The working distance of fiber collimator is related to the distance between fiber end and lens. According to the actual demands, we can determine the parameters of fiber collimator, such as distance between fiber end and lens, beam radius, accuracy, to achieve better performance.


Lens Types of Fiber Collimator

Nearly all types of lens have been used for fiber collimator. They are the fiber lenses, ball lenses, aspherical lenses, spherical singlets and doublets, GRIN (GRaded INdex) lenses, microscope objectives, cylindrical lenses and so on. Under most circumstances, GRIN lens are widely used because of the low cost and small size. However, when it comes to larger beam diameters, spherical singlet or doublet lenses are more suitable for the application. In addition, lens materials are also different. Glass, plastic and silicon are the common lens materials.


Fiber collimator is an effective passive optical component used for laser beam collimating. This article presents some simple facts about fiber collimator, you can take it as a reference for beginners. Selecting the right type of fiber collimator is essential to the performance of network, you should consider your project requirements as important factors. Moreover, although fiber collimator is a small device, it can still be costly in some situations. Your budget limit should also be taken into consideration. Consulting a professional technician for help is always recommended.

Have You Used Optical TAP Cassette Before?

In today’s intelligent data center, real-time monitoring has become an important part to secure the network for better performance. Is there any device that can achieve both data transmission and monitoring at the same time? Certainly, fiber optical TAP (traffic access point) cassette is the ideal solution. This hardware tool enables you to monitor every bit, byte and packet of your data information. If you are not familiar with this type of device, the article is going to explain it to you.

Basics of Fiber Optical TAP Cassette
Fiber optical TAP is an access point installed in networks that provides real-time monitoring of ports. Typically, the data is used to monitor for security threats, performance issues, and optimization of the network. Fiber optical TAP cassette is a passive device that integrates TAP functionality into cable patching system, which requires no power of its own and does not actively interact with other components of the network. Instead of two switches or routers connecting directly to each other, the fiber optic cassette sits between the two endpoint devices connected directly to each of them. Then traffic is copied and once the traffic is tapped, the copy can be used for any sort of monitoring, security, or analytical use. Thus, TAP cassettes are a key component of any visibility system.

TAP cassette

Operation Principle of Fiber Optical TAP Cassette
Optical fiber is designed to send light from a transceiver through a thin glass cable to a receiver on the other end. Instead of connecting directly to each other, each of the two endpoint nodes (switches, routers, database, etc) are connected to network ports on the TAP cassette. A TAP cassette usually integrates both network ports and monitoring ports in a module and it includes an optical splitter, which “splits” off a percentage of the input power and sends it to a monitoring device. As shown in the figure below, we can connect the TAP cassette to the Switch X and Switch Y via network ports and connect TAP cassette to monitoring device via monitoring ports.

TAP cassette
By using the splitter, we can see that a part of TX data of Switch X transmits to RX of Switch Y and another part of TX data of Switch X transmits to monitor. Similarly, a part of TX data of Switch Y transmits to RX of Switch X and another part of TX data of Switch Y transmits to monitor. The monitored traffic is thus separated into two transmit (TX-only) signals, one copy from endpoint A (Switch X), and one copy from endpoint B (Switch Y). The proportional share of light for each path (transmit to network and monitor) is known as the split ratio. The split ratio is written as a combination of two percentages. The first number is designated as the network percentage. The second number is the monitor percentage. They always add up to 100 percent. For example, a common split ratio for traditional 1Gb short-range links is 70/30, where 70% of the light continues to the network and 30% is allocated to the monitor port.

Connecting Your Fiber Optical TAP Cassette
Before you connect the fiber optic cable into a TAP cassette, make sure that the TAP cassette is compatible with the cables. At present, TAP cassettes are mainly available in LC and MTP two port types. Take the MTP TAP cassette for example, and following steps will show you how to connect an optical TAP cassette to your network:

TAP LGX cassette

To connect TAP cassette to the network (in-line links)

  • Step 1, connect MTP network port to switch A using an MTP cable.
  • Step 2, connect another MTP network port to switch B using an MTP cable.

To connect TAP cassette to the monitoring device

  • Step 1, connect TAP monitor port to monitoring device using an MTP cable for switch A monitoring.
  • Step 2, connect another TAP monitor port to monitoring device using an MTP cable for switch B monitoring.

Fiber optical TAP cassette makes it possible to monitor and transmit optical data simultaneously. Technicians are able to gather valuable data analytics and detect network traffic issues in a timely manner. Optical TAP cassette has been widely used in data centers and telecom carrier networks. If you are interested, please visit FS.COM for more information.

The Application of Optical Passive Components in WDM System

Based on the DWDM technology, the all-optical network make full use of fiber optic cables which have huge transmission capacity, it must be the next-generation high reliability, fast speed information network technology. Fiber optic attenuators are widely and important optical passive components, especially in the all-optical network.

Optical attenuator is applied into WDM system upstream and downstream node channel, power balance, EDFA gain flatness, optical communication lines, system evaluation, research and adjustments, correction and so on. It is in accordance with customers’ requirements by absorbing or reflecting off part of the optical power and then reduce the signal power as expectation. It’s position in the optical fiber network just shown in the figure.


Warm Tips:  TX – Transmitter                    RX – Receiver

                     WL – Wavelength Locker       MOD – Modem

                      FM –  Filtration Module       OXC – Optical Cross Connect

                      OADM – Optical Add Drop Multiplexer

In the WDM system, EDFA is a necessary component, it is quite important for achieving all-optical network communication. However, because of the limitation of gaining window ports for EDFA, it makes different wavelengths have different gain multiplier, it leaded to energy imbalance between the channels of a WDM sytstem. Then it will result in following three problems:

  • Received Energy imbalance will beyond the allowed dynamic range finally.
  • Accumulation of SNR imbalance can cause gain of a certain wavelength of BER, it may lower than the required BER (bit error rate).
  • Because of the shortage of the gain, the minimum signal power of the channel may be lower than the sensitivity of the receiver.

In the DWDM optical network which has multiple contact node, such as MAN, the transmission distances and the volume of the business between the different channels are different, each channel’s transmission must be balanced, including power, BER, signal to noise ratio and so on. The application of variable fibre optic attenuator is the first solution in the system.

Moreover, optical attenuators are also important for optical telecommunication link and the test for the system. Fiber optic cable link and the system need to be examined before laying them, then it can insure some performance parameters of the system or link road, so that it is easy to do some optimization test. So we need to simulate the actual situation, mainly the proper attenuation for the signal, then we will find out the actual situation after the long distance transmission.

How the PON Networking infrastructure Support the delivery of the Internet Services

Telecommunications networks are hierarchy organization. House and commerce access is based on wireless and wireline, wireless networks include 2G, 3G, 4G and WiFi, and wireline technologies are those fiber point-to-point (P2P), point-to-multipoint passive optical networks (PONs), copper twisted pair, HFC (hybrid fiber coaxial)  technologies.

Passive optical networks are the basis of Optical Access Networks (OANs) as defined in ITU-T Recommendation G.902, and also of hybrid fiber coaxial networks. PONs are often configured in tree or bus structures. Feeder and distribution fibers, together with the distribution elements in the outside plant, are referred to as Optical Distribution Network (ODN). The different degrees of optical versus electrical access down to the customers for the different fiber-to-the-X(FTTX) access scenarios, where X stands for cabinet (Cab), curb (C), building (B), or home (H). The reference points for the OAN are the service network interface (SNI) and the user network interface (UNI). They are defined in ITU-T Recommendation G.983. The network architecture used to build a PON based FTTx network will typically comply with international standards.

The main PON components include just like, OLT which its full name is Optical line termination and service provider head end in CO, and Remote node just called RN , it mostly passive, containing splitter/combiner or filter, for example, in cabinets, then ONU, it is optical network unit where at customer premises (CP), or in cabinet, etc.

AG.983 compliant PON typically consists of an optical line termination (OLT), which is located at the IPTV data center and a number of optical network terminals (ONTs), which are installed at the end users premises. Note that ONTs May also be installed at different neighborhoods where the optical fiber terminates. In these situations, high speed copper data transfer technologies such as DSL are used to carry the IPTV signals into the end-users’ household.

The OLT uses components such as fiber cable and optical splitters to route network traffic to the ONTs.

Fiber cable, the OLT and the various ONT’s are interconnected by fiber optic cabling. With few transmission losses, low interference, and high bandwidth potential, optical fiber is an almost ideal transmission medium. The core of the fiber optic cable is made of glass and carries data in the form of light wave signals. The diameter of the fiber cable is relatively small and is designed to allow network engineers splice the cable at various locations along the physical route. The purity of today’s glass fiber, combined with improved system electronics in the cable, permits the transmission of high speed services over long distances. In fact, the G.983 standard allows the PON to carry digitized light signals up to a maximum distance of 20 km without amplification.

Optical splitters, the optical splitter are used to split a single optical signal into multiple signals. It achieves this function while not altering the state of the signal; in other words, it does not convert it to electrical pulses. Optical splitters are also used to merge multiple optical signals back into a single optical. These splitters allow up to 32 households to share the FTTx network bandwidth and are typically housed in accessible mechanical closures.

In PONs, several customers are connected to a central office or local exchange via a passive fiber-optic infrastructure. This infrastructure splits into single-mode fibers and passive splitting components (power splitters/combiners and/or WDM filters). PONs work bidirectionally on single fibers, in almost all cases, by using different wavelengths for upstream (US) and downstream (DS).

Fiber cable and optical splitters are “passive” optical components. The use of passive components to guide the light waves through the network eliminates the need for remote powering, which cuts down on operational and maintenance costs.

The main purpose of the ONT is to provide IPTV subscribers with an interface to the PON. It receives traffic in optical format, examines the address contained within the network packets, and converts it into electrical signals. The ONT can be located inside or outside the residence, and is typically powered from a local source, and include bypass circuitry that allows the phone to operate normally in the event of a power failure. The majority of ONTs will include an Ethernet interface for data traffic, an RJ-11 connection for connecting into the home phone system, and a coaxial interface to provide connectivity to the TV. The ONT is also responsible for converting data into optical signals for transmission over the PON. active optical networks (AON) makes use of electrical components between the IPTV end user and the data center. In particular, the AON networking architecture utilizes Ethernet switches that reside between the IPTV data center and the endpoint of the fiber network.

For example, a single piece of optical fiber is run from the backend office to an optical splitter, which is typically located in close proximity to the subscriber’s house. The bandwidth on this fiber is typically shared and is capable of supporting high bandwidth capacities ranging from 622 Mbps all the way up to several gigabytes of data per second.


In addition to the physical components of a PON also illustrates the transmission of three different light wavelengths (channels) over the network. The first wavelength is used to carry high speed Internet traffic. The second wavelength is allocated to carry IO video services and the third wavelength may be used to carry interactive traffic from the subscriber’s home network back to the service provider’s backend equipment. Specialized FTTX filters called wavelength division multiplexers (WDMs) are installed at the data center and inside the OLT that allow a PON to support the transmission of multiple parallel channels or wavelengths on the one piece of fiber. Thus, creating a number of virtual fiber channels over a single fiber pair. Under WDM, the capacity of the network is increased by assigning signals that originate from optical sources to specific wavelengths on the optical transmission spectrum.

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