Understanding OLT, ONU, ONT and ODN

by Fiber-MART.COM

In recent years, Fiber to the Home (FTTH) has started to be taken seriously by telecommunication companies around the world, and enabling technologies are being developed rapidly. There are two important types of systems that make FTTH broadband connections possible. These are active optical networks (AON) and passive optical networks (PON). By far the majority of FTTH deployments in planning and in deployment use a PON in order to save on fiber costs. PON has recently attracted much attentions due to its low cost and high performance. In this post, we are going to introduce the ABC of PON which mainly involves the basic components and related technology, including OLT, ONT, ONU and ODN.

 

First of all, it is necessary to have a brief introduction of PON. In contrast to AON, multiple customers are connected to a single transceiver by means of a branching tree of fibers and passive splitter/combiner units, operating entirely in the optical domain and without power in PON. There are two major current PON standards: Gigabit Passive Optical Network (GPON) and Ethernet Passive Optical Network (EPON). But no matter which type of PONs, they have a same basic topology structure. A Gigabit Ethernet Passive Optical Network (GEPON) system is generally composed of an optical line terminal (OLT) at the service provider’s central office and a number of optical network units (ONUs) or optical network terminals (ONTs) near end users, as well as the optical splitter. In addition, the optical distribution network (ODN) is used during the transmission between OLT and ONU/ONT.

 

Optical Line Terminal (OLT)

OLT is a equipment integrating L2/L3 switch function in GEPON system. In general, OLT equipment contains rack, CSM (Control and Switch Module), ELM (EPON Link Module, PON card), redundancy protection -48V DC power supply modules or one 110/220V AC power supply module, and fans. In these parts, PON card and power supply support hot swap while other module is built inside. The main function of OLT is to control the information float across the ODN, going both directions, while being located in a central office. Maximum distance supported for transmitting across the ODN is 20 km. OLT has two float directions: upstream (getting an distributing different type of data and voice traffic from users) and downstream (getting data, voice and video traffic from metro network or from a long-haul network and send it to all ONT modules on the ODN.

 

Optical Network Unit (ONU)

ONU converts optical signals transmitted via fiber to electrical signals. These electrical signals are then sent to individual subscribers. In general, there is a distance or other access network between ONU and end user’s premises. Furthermore, ONU can send, aggregate and groom different types of data coming from customer and send it upstream to the OLT. Grooming is the process that optimises and reorganises the data stream so it would be delivered more efficient. OLT supports bandwidth allocation that allows to make smooth delivery of data float to the OLT, that usually arrives in bursts from customer. ONU could be connected by various methods and cable types, like twisted-pair copper wire, coaxial cable, optical fiber or Wi-Fi.

 

Optical Network Terminal (ONT)

Actually, ONT is the same as ONU in essence. ONT is an ITU-T term, whereas ONU is an IEEE term. They both refer to the user side equipment in GEPON system. But in practice, there is a little difference between ONT and ONU according to their location. ONT is generally on customer premises.

 

Optical Distribution Network (ODN)

ODN, an integral part of the PON system, provides the optical transmission medium for the physical connection of the ONUs to the OLTs. Its reach is 20 km or farther. Within the ODN, optical fibers, fiber optic connectors, passive optical splitters, and auxiliary components collaborate with each other. The ODN specifically has five segments which are feeder fiber, optical distribution point, distribution fiber, optical access point, and drop fiber. The feeder fiber starts from the optical distribution frame (ODF) in the central office (CO) telecommunications room and ends at the optical distribution point for long-distance coverage. The distribution fiber from the optical distribution point to the optical access point distributes optical fibers for areas alongside it. The drop fiber connects the optical access point to terminals (ONTs), achieving optical fiber drop into user homes. In addition, the ODN is the very path essential to PON data transmission and its quality directly affects the performance, reliability, and scalability of the PON system.

 

Conclusion

There are different types of OLT, ONU, ONT equipments for GEPON, which are the new generation PON equipments and mainly applied by telecommunication operators in FTTH project. All these equipment are provided in fiberstore and have the characteristic of high integration, flexible adaption, reliability and capable of providing QOS, web-management as well as flexible enlarging capacity. For more information, please contact us over sales@fiber-mart.com.

Data Center Design for 40G/100G Network

1G and 10G data rates are not adequate to meet the future needs of high-bandwidth appli- cations. The requirement for higher data rates is being driven by many factors. Switching and routing, virtualization, convergence and high-performance computing environments are examples of where these higher network speeds will be required within the data center environment. Additionally, Internet exchanges and service provider peering points and high-bandwidth applications, such as video-on-demand will drive the need for a migration from 10G to 40/100G interfaces.

Bandwidth

OM3 and OM4 fibers were selected as the only multimode fiber for 40/100G consideration. The fibers are optimized for 850 nm transmission and have a minimum 2000 MHz∙km and 4700 MHz∙km effective modal bandwidth (EMB), respectively.
Two EMB measurement techniques are utilized today for the bandwidth measurement. The minimum effective modal bandwidth calculated (EMBc) method offers the most reliable and precise measurement compared to the differential modal delay (DMD) mask technique. With minEMBc, a true scalable bandwidth value is calculated that can reliably predict performance for different data rates and link lengths. With a connectivity solution using OM3 and OM4 fibers that have been measured using the minEMBc technique, the optical infrastructure deployed in the data center will meet the performance criteria set forth by IEEE, Fibre Channel and InfiniBand for bandwidth.

Insertion Loss

Insertion loss is a critical performance parameter in current data center cabling deploy- ments. Total connector loss within a system channel impacts the ability of a system to operate over the maximum supportable distance for a given data rate. The 40/100G Ethernet standard specifies the OM3 fiber 100 m distance maximum channel loss to be 1.9 dB, which includes a 1.5 dB total connector loss. The OM4 fiber 150 m distance maximum channel loss is 1.5 dB, which includes a 1.0 dB total connector loss budget.
The insertion loss specifications of the MPO connectivity components should be evalu- ated when designing data center cabling infrastructures. With low-loss MPO connectivity components, maximum flexibility can be achieved with the ability to introduce multiple connector matings into the connectivity link such that structured cabling architectures can be supported.

Skew

The IEEE 802.3ba standard includes an optical media skew of 79 ns. Optical skew, the difference in time of flight between light signals traveling on different fibers, is an essential consideration for parallel optics transmission. With excessive skew, or delay, across the various channels, transmission errors can occur. Skew testing on MPO connectivity solu- tions has demonstrated compliance to a strict 0.75 ns skew requirement as defined in the InfiniBand standard. Deployment of a connectivity solution with strict skew performance ensures compatibility of the cabling infrastructure across a variety of applications. When evaluating optical cabling infrastructure solutions for 40/100G applications, selecting one that meets the 0.75 ns skew requirement ensures performance not only for 40/100G, but also for InfiniBand.

Additionally, low–skew connectivity solutions validate the quality and consistency of cable designs and terminations to provide long-term reliable operation.

Five Basics About Fiber Optic Cable

A fiber optic cable is a network cable that contains strands of glass fibers inside an insulated casing. They’re designed for high performance data networking and telecommunications. Fiber optic cable carry communication signals using pulses of light, faster than copper cabling which uses electricity. They are becoming the most significant communication media in data center. Then how much do you know about them? This post serves as a guide for beginners.

Fiber Components

The three basic elements of a fiber optic cable are the core, cladding and coating. Core is the light transmission area of the fiber, either glass or plastic. The larger the core, the more light that will be transmitted into the fiber. The function of the cladding is to provide a lower refractive index at the core interface, causing reflection within the core. Therefore the light waves can be transmitted through the fiber. Coatings are usually multi-layers of plastics applied to preserve fiber strength, absorb shock and provide extra fiber protection.

Fiber Type

Generally, there are two basic types of fiber optic cables: single mode fiber (SMF) and multimode fiber (MMF). Furthermore, multimode fiber cores may be either step index or graded index.

Single mode and multi-mode fiber-optic cables

Single mode optical fiber is a single strand of glass fiber with a diameter of 8.3 to 10 microns that has one mode of transmission. The index of refraction between the core and the cladding changes less than it does for multimode fibers. Light thus travels parallel to the axis, creating little pulse dispersion. It’s often used for long-distance signal transmission.

Step index multimode fiber has a large core, up to 100 microns in diameter. As a result, some of the light rays that make up the digital pulse may travel a direct route, whereas others zigzag as they bounce off the cladding. These alternative pathways cause the different groupings of light rays to arrive separately at a receiving point. Consequently, this type of fiber is best suited for transmission over short distances.

Graded index fibers are commercially available with core diameters of 50, 62.5 and 100 microns. It contains a core in which the refractive index diminishes gradually from the center axis out toward the cladding. The higher refractive index at the center makes the light rays moving down the axis advance more slowly than those near the cladding.

Fiber Size

Single mode fibers usually has a 9 micron core and a 125 micron cladding (9/125µm). Multimode fibers originally came in several sizes, optimized for various networks and sources, but the data industry standardized on 62.5 core fiber in the mid-80s (62.5/125 fiber has a 62.5 micron core and a 125 micron cladding. It’s now called OM1). Recently, as gigabit and 10 gigabit networks have become widely used, an old fiber design has been upgraded. 50/125 fiber was used from the late 70s with lasers for telecom applications. 50/125 fiber (OM2) offers higher bandwidth with the laser sources used in the gigabit LANs and can allow gigabit links to go longer distances. Laser-optimized 50/125 fiber (OM3 or OM4) today is considered by most to be the best choice for multimode applications.

Basic Cable Design

The two basic cable designs are loose-tube cable, used in the majority of outside plant installations, and tight-buffered cable, primarily used inside buildings.

The modular design of loose-tube cables typically holds up to 12 fibers per buffer tube with a maximum per cable fiber count of more than 200 fibers. Loose-tube cables can be all dielectric or optionally armored. The modular buffer-tube design permits easy drop-off of groups of fibers at intermediate points, without interfering with other protected buffer tubes being routed to other locations.

Tight-buffered cables can be divided into single fiber tight-buffered cables and multi-fiber tight-buffered cables. single fiber tight-buffered cables are used as pigtails, patch cords and jumpers to terminate loose-tube cables directly into opto-electronic transmitters, receivers and other active and passive components. While multi-fiber tight-buffered cables also are available and are used primarily for alternative routing and handling flexibility and ease within buildings.

Connector Type

While there are many different types of fiber connectors, they share similar design characteristics. Simplex vs. duplex: Simplex means 1 connector per end while duplex means 2 connectors per end. The following picture shows various connector styles as well as characteristics.

Summary

Ultimately, what we’ve discussed is only the tip of the iceberg. If you are eager to know more about the fiber optic cable, either basics, applications or purchasing, please visit www.fiber-mart.com for more information.

Multimode simplex SC to SC fiber optic patch cord

We are fiber optic patch cord supplier, we offer fast delivery for Multimode simplex SC to SC fiber optic patch cord.

Multimode simplex SC to SC fiber optic patch cord Ordering information:

Termination connectors: FC,SC,MU,LC,ST, D4,DIN,E2000 MT-RJ,MPO ,SMA

Ferrule Interface type: PC, UPC, APC

Fiber diameter(mm): Φ 0.9, φ 2.0, Φ 3.0

Fiber cores: duplex fiber core,Simplex fiber core

Fiber type: multimode(50/125)/(62.5/125) ,Singlemode(G. 652, G655)

Cable length: can be customized

We are fiber optic patch cord company,Fiber optic patch cord is one of most commonly used components in fiber optic network,SC SC multimode simplex patch cord is widely applied in Telecommunication Networks ,Gigabit Ethernet and Premise Installations .

Multimode simplex SC to SC fiber optic patch cord is with SC connector,The SC connector is with a locking tab on the cable termination, it is a push and pull type fiber optic connector. It features low cost, simplicity, and high durability.SC fiber optic patch cord has an advantage in keyed duplexibility to support send/receive channels.We are SC SC multimode simplex patch cord company and manufacturer,we offer fast delivery and custom made service.

Waterproof Fiber Optic Cables

fiber-mart.com has developed a new type of waterproof fiber optic cable that has been manufactured according to IEC standards. Fiber optic cables are typically used to connect fiber optic cable with fiber optic equipment. The product possesses low insertion loss, repeat push-pull performance and high return loss and these qualities make the cable user-friendly.

 

Waterproof fiber optic patch cables are designed to fit for outdoor applications. The waterproof fiber optic cables are with strong PE jacket and armored structure, they can resist high temperature and suit to use in harsh environment.

We supply both single mode and multimode waterproof fiber cables, custom cable assemblies are available. Waterproof fiber optic cable assemblies include waterproof fiber optic cable and waterproof fiber optic patch cord.by adopting the special structure cables and connectors, these fiber cable assemblies are widely used in CATV and other applications.

 

Waterproof Fiber Optic cables are widely used in data transmission network, typical types are with 2 fiber cores, 4 fiber cores or 8, 12 fiber cores. fiber-mart.com produce the fiber optic waterproof cables strictly according to IEC standards, the products feature low insertion loss, high return loss, good interchangeability and repeat push-pull performance, which make them easy to use. The waterproof fiber optic cables are with strong PE jacket and waterproof sealed head connectors; they can be used in harsh environment.

 

Waterproof Fiber Optic cables Features:

Various kinds of connect interfaces optional such as SC,FC,ST,LC, etc.

Ceramic ferrules, PC, UPC, APC polishing optional

Low insertion loss, high return loss

Waterproof

Out diameter of inner fiber: 3.0mm, 2.0mm, 0.9mm

Why Use Tunable DWDM SFP+ Transceivers?

http://www.fiber-mart.com/fiber-optic-transceivers-sfp-transceivers-c-1_2.htmlThe tunable DWDM SFP+ is one kind of DWDM SFP+ transceivers. They both can be used in the DWDM system. In the market, tunable DWDM SFP+ transceivers are often between two and four times more expensive than DWDM SFP+ transceivers. Thus, many may think DWDM SFP+ transceivers are enough in the DWDM system and wonder why tunable DWDM SFP+ transceivers are also needed. This post will introduce what is tunable DWDM SFP+ transceiver and explain why they need to be used in DWDM systems in details.

 

What’s Tunable DWDM SFP+ Transceiver?

Tunable SFP+ transceivers are a new technology that is in development for a few more years due to the limiting power specifications of the SFP+. They are only available in DWDM form because the CWDM grid is too wide. So a tunable SFP+ transceiver is also called tunable DWDM SFP+ transceiver.

 

The tunable DWDM SFP+ transceiver is equipped with an integrated full C-Band 50GHz tunable transmitter and a high performance PIN receiver to meet the ITU-T (50GHz DWDM ITU-T Full C-band) requirements. It shares the same hot–pluggable SFP+ footprint as DWDM SFP+ transceiver. The major difference between them is that DWDM SFP+ has a fixed wavelength or lambda while the tunable DWDM SFP+ can adjust its wavelength on site to the required lambda. Tunable DWDM SFP+ transceivers enable us to change wavelengths unlimited within the C-band DWDM ITU Grid and can be applied in various types of equipment such as switches, routers and servers.

 

Why Tunable DWDM SFP+ Transceivers Are Used in DWDM Systems?

 

In traditional DWDM systems, fixed-wavelength DWDM SFP+ transceivers are commonly used as light sources in optical communication field. However, as the continuous development, application and promotion of optical communication systems, the disadvantages of DWDM SFP+ transceivers have been gradually revealed. The followings are why tunable DWDM SFP+ transceivers are also needed in DWDM systems:

 

On the one hand, it is essential to prepare backup DWDM SFP+ transceivers for each DWDM wavelength to avoid unnecessary breakdown. In traditional DWDM systems, a small number of extra DWDM SFP+ transceivers are enough. However, with the development of technology, the number of wavelengths in DWDM 50GHz now has reached the hundreds. This means people have to provide up to hundreds of backup DWDM SFP+ transceivers, which will greatly increase the operating cost. Tunable DWDM SFP+ transceivers provide equipment manufacturers and operators with great flexibility, achieving the optimization for the overall network performance and greatly reduce the demand of existing operators for DWDM SFP+ transceiver inventory.

On the other hand, in DWDM systems, it may be required to use a large number of DWDM SFP+ transceivers with different wavelengths to support the dynamic wavelength assignment in optical network and improve network flexibility. But the usage rate of each transceiver is very low, resulting in a waste of resources. The arrival of tunable DWDM SFP+ transceivers has effectively solved this problem. With tunable DWDM SFP+ transceivers, different DWDM wavelengths can be configured and output in the same light source, and these wavelength values and intervals all meet the requirements of ITU-T (50GHz DWDM ITU-T Full C-Band).

 

Conclusion

 

Featuring for flexibly selecting working wavelength, tunable DWDM SFP+ transceivers have very large practical value in optical fiber communication wave division multiplexing system, optical add-drop multiplexer and optical cross-connection, optical switching equipment, light source parts and other applications.

 

Raman-off gain 10dB FM-RA Series Raman Amplifier

Raman-off gain 10dB FM-RA Series Raman Amplifier

Raman-off gain 10dB FM-RA Series Raman Amplifier is high power Raman Amplifier which is used in low noise, Long span or high speed Optical Transmission system. Using transmission fiber as the gain medium to form distributed to enlarge, reduce system noise and will get best gain and noise index mix the our EDFA product.

Each Pump output power can be adjustable independently which is suitable for a variety network applications and to enlarge the bandwidth.

"Intelligent network management system. Perfectly network interface: Ethernet, RS-485 and RS-232 network，and the open network management interface ensure the connectivity with all other network management system. "

Features

• Gain: 10dB
• Connectors: SC/UPC, SC/APC, FC/UPC, FC/APC, LC/UPC, LC/APC, ST/UPC and ST/APC connectors are available
• 1U 19” rack mount structure for easy installation
• Redundancy hot swap power: 110V/220V mixed with 48V
• Distributed low-noise amplification
• Easy control and operate: Dual CPU process control Loops and the upper Interface respectively
• Perfect network Management interface: Ethernet RS-485 and RS232
• SNMP Network management Or provide SNMP Mib
• Single channel, DWDM or C+L band is available
• Intelligent temperature control system: power consumption and hot Radiation reduce 30% than common products
• Pump polarization-Independent design
• Compatible with Bellcore GR-1312-CORE
• High stability and reliability
• 10 years of operation life
• 3 years warranty
• OEM is available

Application

• SDH, ATM telecom long distance optical Transmission
• Analog digital TV long distance Optical Transmission system
• Long span system
• 10G, 40G system

Specification

Parameters	Symbol	Min	Typ	Max	Unit
Operation Wavelength	λc	1525	1550	1565	nm
Pump wavelength	λp	1425	1	1505	nm
Pump output power	Po		500	1000	mW
On/OFF Gain	G	6		14	dB
Gain Flatness	FL		1		dB
Polarization Dependent Gain	PDG			0.3	dB
PMD	PMD			0.3	ps
Relative Noise Figure	NF			0	dB
Power Supply	Vps	85/170	110/220	132/264	VAC
Consumption	P			18	W
Operating Temperature	Tw	-5		60	℃
Storage Temperature	Ts	-40		80	℃
Humidity		10		85	%