Functions of ONT and OLT in GPON Network

Gigabit passive optical network (GPON) is a point-to-multipoint access mechanism providing end users with the ability to consolidate multiple services onto a single fiber transport network. To realize this technology, many devices are used to support the network, such as optical splitter, ONT, OLT, etc. In this article, we will mainly discuss the functions of ONT and OLT in GPON network.


Functions of ONT

Optical network terminal (ONT) is an optical modem that connects to the termination point with an optical cable. It is used at end user’s premise to connect to the PON network on one side and interface with the user on the other side. Data received from the customer end is sent, aggregated and optimized by the ONT to the upstream OLT. ONT is also known as optical network unit (ONU). ONT is an ITU-T term, while ONU is an IEEE term. They both refer to the user side equipment in GPON network. A small difference between them might be the application locations. ONU can work in different temperature and weather conditions.


Functions of OLT

Optical line terminal (OLT) is the endpoint hardware equipment located in a central office of the PON network. Its basic function is to control the float information in optical distribution network (ODN) to go in both directions. OLT converts the standard signals used by fiber optic service (FiOS) to the frequency and framing used by PON system. In addition, it coordinates the multiplexing between the ONT conversion devices. There are two float directions for OLT system. One is the upstream direction to distribute different types of data and voice traffic from users. The other is the downstream direction which gets data, voice and video traffic from metro network or from a long-haul network and sends it to all ONT modules on the ODN.


How to Add or Delete ONT on OLT?
Way to Add ONT on OLT

If the password of an ONT is obtained, you can run the ONT add command to add the ONT offline. However, if the password is unknown, you can run the port portid ont-auto-find command in the GPON mode to enable the ONT auto-find function of the GPON port, and then run the ONT confirm command to confirm the ONT. When the ONT is added, you need to run the display ONT info command to see the current status of ONT. If the control flag is active, run state is online, config state is normal, and match state is match, then the ONT adding process is successful.

Way to Delete ONT on OLT

When you need to delete the ONT on OLT, please use the delete command. Then ONT configuration data is deleted with the deletion of the ONT and the online ONT is forced offline. ONT can’t be deleted when it has been configured with other services. You need to unbind the service first before delete the ONT.

How to Troubleshoot ONT?

To troubleshoot the ONT, you should remember that the most important step is to connect your computer directly to the ONT to see if the problem goes away. You can use the Ethernet cable for connection. If the problem still exists, you can reconnect the ONT power supply to clear its internal cache. If the network can not be restored after the above methods, maybe you need to consult professionals for help.


ONT and OLT are indispensable components in the GPON network system. If you are considering to purchase the ONT or OLT devices, FS.COM is a good place to go. Different types of ONT and OLT equipment are provided with high integration, flexible adaption and great reliability to meet all your requirements.

Related Article: Comparison Between EPON and GPON

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, 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 Optical TAP Cassette
Optical TAP is an access point install 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. 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 optical TAP 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 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 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 a MTP cable.
  • Step 2, connect another MTP network port to switch B using a MTP cable.

To connect TAP cassette to the monitoring device

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

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.

Overview of Fiber Optic Loopback

When testing the transmission equipment, fiber optic loopback device is often used as the testing tool. It is known as the routing of electronic signals, digital data streams, or flows of items back to their source without intentional processing or modification. Fiber optic loopback is widely used for various applications. In terms of telecommunication, loopback is a hardware or software method to feed a received signal or data back to the sender. It is very useful for solving physical connection problems. In this article, the author will especially emphasize the using of loopback in fiber optic communication. Hope it can provide some help for your application!

Types of Fiber Optic Loopback

So, what is exactly the fiber optic loopback? By diagnosing the problems of optical equipment, fiber optic loopback provides an easy way to test the performance of the optical network devices. Generally, fiber optic loopback cable and fiber optic loopback module are both fiber optic loopbacks. Fiber optic loopback cable is the traditional fiber optic loopback with a visible cable. It is equipped with two fiber optic connectors on each end of the cable. When sticking the connectors together, the cable will shape like a loop. As for fiber optic loopback module, the biggest difference is that it has a enclosure to protect the inside cable. And the looped space is reduced for an easier usage and economic package.


You may find that loopback also has different types of optical connectors and fibers. Categorized by connectors, fiber optic loopback has SC, LC, MTRJ, E2000 types, etc. LC fiber optic loopback complies with the RJ-45 style interface. Having a low insertion loss, low back reflection and high precision alignment, LC fiber optic loopback is widely used all over the world. Another frequently used type is SC fiber optic loopback. Its connector is compliant to IEC, TIA/EIA, NTT and JIS specifications. Now it is the most popular loopback with low cost but high performance. In addition, to separate by fiber types, single-mode loopback (9/125) and multimode loopback (50/125, 62.5/125)  are deployed for the application.

Fiber Optic Loopback Testing

Typically, a loopback test is a test in which a signal is sent from a communication device and looped back to the device as a way to determine whether it is functioning well or as a way to troubleshoot a defective node in the network. As for fiber optic loopback testing, optical loopbacks are used to verify the operational reliability of the device. Using fiber optic loopback cable or fiber optic loopback module for data transmission, the signal emitted by the device is looped from the transmit (Tx) end of an active component back to the receive (Rx) end of the same component.


When it comes to practical application, fiber optic loopback test is often employed for checking fiber optic transceivers. Since transceiver has two ports for receiving and transmitting the light signal, it is necessary to test the ports to see whether they are still under operation. Thus, fiber optic loopback test is the most convenient way for transceiver maintenance. The testing process is by routing the laser signal from the transmitter port back to the receiver port. Then the transmitted pattern is compared with the received pattern to make sure they are identical and have no error.


In a word, fiber optic loopback is basically a patch cord used for fiber optic loopback testing. Similar to other cables, it also has multiple classifications of fiber types, connector types for different needs. The deployment of fiber optic loopback components has greatly saved the trouble for device checking. There is no doubt that using fiber optic loopback is an effective method in fiber optic communication.

Related Article: Which Fiber Loopback Should I Use for My Transceiver?

Another Point of Thought about Fiber Optics Which Take WDM as an Example

We usually defined unfamiliar things as mystical, or difficult to understand but must be associated with the creation of that which is not familiar and already understood. In fact, I think that the familiar thing or regular thing you often do it. Maybe you do not really understand it completely. You just know what you need it to do. For example, when you go up early to work and ready to go to have a shower, Do you know all the things that had to happen for that hot water to come out of the shower? Possiblely not, you just know that once you turn on the switch, you will have a warm shower. Have a think of all the happened things in a normal day, you may not have second though because they are so familiar. Turn on the light, Watch TV, have a call, send an email and so on.

This always makes me think about that when a new technology is brought in the daily life, we always keep evasive attitude towards it, and the improvements of benefits and so many converiences it brings to our daily life. Well, I set the fiber optics product as an example. WDM, wavelength division. Related product: 8 channel cwdm multiplexer. See the figure. They have a similar feature is that people all used it but they are not aware that they are. Well, if you ask me about what the optical wavelength division multiplexing is, I will be glad to tell you the answer in a special way.


While in the copper cabling, if you want to get multiple signals on the same cable, it needs various of technical phenomena and acronyms which you may think it too boring. Such as ASK, CPFSK, DTMF, FSK, MFSK, OFDM and others. In fact, it just used in the old common telephone.

white light

While in the optical wavelength division multiplexing, it likes this. When go out and see the bright sunny day, the light from the Sun is basically white color. However, you take that light and shine it through a triangular glass prism and voila, you are presented with a rainbow of different colors! Well, those colors that are visible to us. We all know scientists divided it as Red, Orange, Yellow, Green, Violet, Indigo and Blue.  Like the figure. As you can see, visible light is actually just a sliver of the total light spectrum. In fiber optics, we use the light at the near infrared side starting at 850nm all the way out to the far infrared side around 1620nm. Each color is related to its particular wavelength. For example, the color green has a wavelength between 495nm – 570nm in the visible spectrum. So, in its simplest form of optical fiber, we take an electrical signal and convert it to a wavelength of light. Then we combine several different wavelengths (multiplexing), each carrying its own signal and transfer it over a glass fiber which so small as a human hair. After you form a habit that understands a technology from a familiar thing which you use it everyday, you will find many differences and more interests in your common life.

Fiberstore’s several important fiber optic product categories

Sometimes you know, whenever inside a fiber optic network system, the requirement occurs to lessen or even stability the ability from the gentle sent in one gadget to a different gadget. Nicely, the fiber optic attenuator can be used in such instances. They could manage the actual result from the fiber gentle energy degree. fiber optic attenuator are utilized with regard to decreasing the ability from the gentle within the fiber optic system.

fiber optic attenuator

The fiber Optic Attenuator can be used slow up the energy inside a optical signal. Obtainable in 1310nm in order to 1550nm. The actual optical attenuator is really a man in order to woman settings as well as connectorized having a FC, SC/APC, ST, PC, LC, UPC, MU, FC/APC, SC, LC/APC, set worth connect kind fiber optic attenuators, inline fiber optic attenuators, adjustable fiber optic attenuators. Typical attenuation ideals tend to be 5dB, 10dB, 15dB as well as 20 dB however all of us share just about all dimensions through 1dB in order to 25db.

Attenuation is actually losing optical energy because gentle moves lower the fiber. It’s calculated within sound levels (db/km). On the arranged range, the fiber having a reduce attenuation enables much more capacity to achieve it’s recipient than the usual fiber along with greater attenuation. Nicely, there’s a brand new item, Fiberstore give a moderate with regard to modifying the actual transmission. The look is actually perfect for set up in to OEM gear. In-line attenuators tend to be avaiable along with attenuation ideals which range from 1-20 dB and may end up being ended along with any kind of solitary setting connection or even remaining unterminated with regard to splicing.

Fiberstore provide 2 kinds of  fiber optic attenuators, set fiber attenuators make reference to the actual attenuator that may slow up the energy associated with fiber gentle in a set worth reduction, for instance, 5dB. Whilst flexible fiber optic attenuator make reference to the actual attenuator that may produce the flexible Reduction towards the fiber optic hyperlink. All of us provide fiber attenuator sequence consist of: SC,FC,LC,ST,MU,SC / APC,FC/ APC, solitary setting fiber optic attenuator as well as multimode fiber optic attenuator obtainable. The fiber optic attenuators tend to be produced based on worldwide regular and therefore are suitable for the actual fiber optic items now available within the worldwide marketplace. fiber optic attenuators could be made to make use of along with types of fiber optic fittings. the actual attenuators could be woman in order to woman which is sometimes called bulkhead fiber optic attenuator or even man in order to woman that is also known as the connect fiber optic attenuator. An additional kind inline fiber optic attenuator was created along with a bit of fiber optic cable television from any kind of duration as well as fittings tend to be set up since the clients ask for.

A good optical splitter is really a unaggressive gadget which divides the actual optical energy transported with a solitary enter fiber in to 2 result materials. The actual enter optical energy is usually divided equally between your 2 materials. This kind of optical splitter is actually a Y-coupler. Nevertheless, a good optical splitter might deliver the actual optical energy transported through enter energy within an unequal method. A good optical splitter might divided the majority of the energy in the enter fiber in order to among the result materials. Just a tiny bit of the ability is actually combined to the supplementary result fiber. This kind of optical splitter is actually a T-coupler, or even a good optical faucet. Fiberstore’s optical splitter is actually broadly recognized as well as utilized in unaggressive optical systems, specifically for situations in which the divided settings is actually scaled-down (1×2, 1×4, 1×8, 1×16, 1×32 fiber splitter and so on.)

Fiberstore system press converters. Utilized like a ethernet in order to fiber converter. The actual press converters may change indicators amongst Ethernet, Quick Ethernet, Gigabit Ethernet, T1/E1, DS3, ATM, Sixth is v. thirty-five, and so on. Fiberstore systems may be the recognized professional within the press converters region; their own changeover systems press converters consider probably the most component on the planet marketplace with this area.

media converter

Fiberstore’s ethernet media converter is utilized within Cisco Techniques, IBM, Nortel, Ms as well as ADC. By utilizing the press converters, these types of globe top businesses reduce their own wiring price. Depending on Changeover Stage Program benefits, customers might conserve the price whilst don’t break down the actual system overall performance. Fiberstore try to work along with user’s been around system gear without having impacting it’s look as well as entire overall performance. Fiberstore press converters tend to be becoming a lot more utilized all over the world. The top quality as well as dependable fiber optic press converters can be found in many types. If you don’t Begin to see the kind you are searching for, after that simply deliver Fiberstore a fast e-mail as well as we’ll have the ability to possibly find the precise kind you’ll need or even we’ll produce this.

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