Transceivers

What are the main components of a Local Area Network (LAN)?

Before digging deeper in the Local Area Networks, let’s start from the basics. A Local Area Network Is a group of devices that share a common communication path to the Internet or are commonly connected to a server, within a certain location and distance, such as head office or commercial establishment. These devices can also share resources between themselves in the same LAN. The Local Area Network can serve in a small office with two or three people and in a large building with hundreds of people. In the past years Local Area Networks were utilizing the Ethernet and Wireless specifications. Only in the last couple of years the Local Area Networks introduced the utilization of fiber optic connections. Ethernet is a specification for physically connecting the whole network and devices together in the LAN with the help of copper cables and Wireless specification uses radio waves to connect the same devices to the LAN.

For a successful connection and proper functioning, the Local Area Network must be made of at least six vital components:

  • A network adapter- this is a network adapter, or most commonly known as a network card (Network Interface Controller- NIC), that has the task to convert data into electrical signals and vice-versa. Although today every computer has this network adapter integrated in the motherboard, in the early rise of computers this wasn’t the case and network cards had to be bought separately and fitted on the motherboard. The network access element of its job is called a MAC or Media Access Control, widely known also as a physical address of a device. The MAC represents the serial number of the network adapter. The wireless equivalent of the network card is called a Wireless Network Interface Controller.
  • A wired medium- In the era of the Ethernet, every wired network connection has the need of cables. The most commonly used cable in Local Area Networks is the RJ45 Ethernet Cable. Other than this, other cables that could be used in Local Area Networks are twin-axial, Shielded Twisted Pair, Multi-mode fibers (MMF) and Single-mode fibers (SMF) for optical connectivity. When it comes to Wireless networks there is no need of network cables as the wireless device transmits radio waves from its WNIC.
  • Cable connectors- Today the most widely used cable connector is the RJ45. At the moment every computer in the world by default has a RJ45 port.
  • Power Supply- Both wired and wireless Local Area Network have the need of power. This is needed because wired networks use the power to convert electrical signals into data and wireless networks use the current to convert data signals into radio waves.
  • Router/Switch- In wired networks, one computer can’t connect to multiple other computers without the help of some kind of splitter. To play the role of the splitter the switch was developed. The switch repeats the signals gotten from one computer and sends them through other ports which are connected to other computers with an Ethernet cable in the same Local Area Network. Routers are a more sophisticated devices that are used to forward data traffic out of the LAN and out on the Internet or to another LAN. Switches use MAC addresses to distinguish the devices connected to them and routers use IP addresses. There is no wireless switch developed however the wireless equivalent of a router is called a wireless router.
  • A network software- this software that is installed on every device has the capability to convert the data into a packet. Then the packet is sent to its destination with the help of a combination of the MAC address and IP address. This packet then travels around the Local Area Network through various switches and routers until it gets to the destination.

The Local Area Network has the task to keep the customers connected to the Internet and provide them with the bandwidth they need for a fast and stable connection. However, with the development of new technologies and applications and the spread of the Internet throughout the world, the need for high speed Internet over a long distance has become essential. The new technology used in Local Area Networks that provides high bandwidth over long distance Internet is the fiber optic solution. This solution utilizes the optical light and optical fiber to transmit the data from one to another device. The data is sent and received with the help of optical lasers integrated into an optical module, also called a transceiver, down an optical cable with one or a couple of optical strands inside. This cable is connected to another transceiver or networking device with capability to convert the optical light into data.

Even though the cost for deploying a fiber optic solution is much bigger, the advantages and gains in performance are enormous. The most obvious and key characteristic of fiber optic networks is the bandwidth they can provide. Even though, heavy copper connections compared to optical connections, grow and continue to be developed to provide longer distances, they are slowly but surely substituted with optical connections. With today’s technology fiber optic equipment can provide many times more bandwidth with ease and at the same time consuming less power than the standard copper connections. Another key difference is the possibility for higher port density than Ethernet cables. The amount of LC optical ports that can be aligned on a networking device is much bigger than the amount of RJ45 ports due to its bigger and bulkier size. When we include the MPO solution in this equation which can have even 12 lines in a small optical connector, the sky is the limit.  

For the optical connection in the Local Area Network to work at maximum performance we need an optical equipment. The key optical components are optical transceivers and optical cables:

  • The optical transceiver is a module with the task to convert electric input into optical light. This light with the help of optical lasers (chips) is then sent down the optical cable. These transceivers, depending on their Form-factor, can provide speeds of up to 100 GB/s at distances up to 160 kilometers. They are commonly installed in a networking device (a switch) and because they are hot-swappable, their installation is simple. Keep in mind that optical transceivers are very sensitive to dust and other particles so handling them with care is a must.
  • The optical transceivers send the optical data down an optical cable. In fiber optic networks the cables are divided into two segments: Multi-mode and Single-mode fiber cables. Multi-mode cables are used for short range fiber optic connections due to their bigger core and the distance depends on the type of the fiber itself, OM1, OM2, OM3 or OM4. Single-mode cables are used in a long range fiber optic connections due to their much tighter core.

Fiber optic networks offer much larger distance limit when compared to copper connections. Most commonly, with copper connections, a repeater or switch must be installed at regular intervals, around 100 meters, to amplify the signal so it doesn’t degrade too much. In a long run this comes out costly for the companies and it requires big effort for installation and maintenance. With fiber optic connections the transmission distance is much greater. A Single-mode cable has the capability to go up to 160 kilometers when combined with the correct equipment and 160 kilometers is enough for a direct connection from the primary server room where the core is located to the final destination. Another advantage for the fiber optic connections is their endurance. Even though various physical stress can damage them, they are very resilient to radio frequencies and magnetic interference. Fiber optics are not conductive and, unlike the copper connections, if a lightning strikes the cables won’t conduct the current to the device and damage it so there is no need for deploying a lightning protection. Finally, fiber optic cables are a lot lighter than copper cables making them easy for transportation and installation.

Today with the great bandwidth demand the companies are deciding to upgrade to fiber optic networks even though the initial cost is bigger. They are convinced that in the long run the fiber optic networks are the future of networking. And with the help of fiber media converters they can allow their existing copper network to communicate with the newly deployed fiber optic solution seamlessly.

What Color Differences do Fiber Optic Patch Cords have

Fiber users like data centers, service providers and small business uses single mode and multi-mode fiber together in the premises. Since there is varieties of fibers like 62.5/125 and 50/125 in multimode and single mode fibers, which is making managing the cable plant more difficult. There are many users which get confused and not getting required results when installing the fibers. At the end their network gets problematic by using wrong type of fiber.

To overcome the above discussed problem, the Telecommunications Industry Association (TIA) introduced color coding to distinguish between the fibers of different kinds. Its recommendation are as follow:

Single mode fiber: single mode fiber are always covered with Yellow color jacket. Yellow color is assigned for single mode fiber. The color of connector for single mode fiber however depends upon the type of connector. For PC/UPC connectors Blue color connectors are used, but when single mode fibers are used with APC connector, Green color connectors are suggested.

Multi-mode fibers: multi-mode fiber are of different kinds 62.5/125 µm and 50/125 µm. OM1 multi-mode fibers 62.5/125 µm are colored with Orange color, their connectors are Beige in color. OM2 multi-mode fibers 50/125 m are also colored Orange, their connectors however are Black in color. OM3 fibers on other hand are in Aqua color, OM3 connector is Aqua color but connector body is Black in color. OM4 fibers are also Aqua in color, but their connectors are Beige in color.

What is SFP+ or a SFP transceiver

SFP stands for small form-factor pluggable it is a compact hot pluggable transceiver used for both telecom and the data applications. LC connectors are used to connect fibers to SFPs. SFP module has two sides, first side known as transmitter it has laser for transmitting and other side known as receiver side has a photo detector. So basically SFP is a transceiver module since it has transmitter and the receiver in a single unit.

SFPs are not standardized by any single body, but relatively are specified by a multi source agreement also called MSA. It is an agreement between several manufacturers to make products which are compatible among different vendors. SFP designed based on the bigger gigabit interface converter (GBIC) interface, but it has a much smaller size in order to increased port density, that is why SFP is also called mini- GBIC.

SFP modules are used in all types of network applications like data networks, telecommunication networks, SAN as well as SONED/SDH.

Typical SFP modules can be classified based on the working wavelengths and its working distance so let's take a look at the list here:

For multimode fibers the SFP modules called SX (short reach) module, it use 850 nanometer wavelength. The distance that SX modules support depend on the network speed, for 1.25 gigabit per second speed the distance achieved is about 550 meters, whereas for 125 gigabit per second speed it supports up to 150 meters

For single mode fiber side there are lots of choices, following are the most common types:

For single-mode fibers the SFP modules called LX (long reach) module use 1310 nanometer wavelength laser and supports up to 10 kilometer. EX module use 1310 nanometer wavelength laser and supports up to 40 kilometer. ZX module use 1550 nanometer wavelength laser and supports up to 80 kilometer. EZX module use 1550 nanometer wavelength laser and supports up to 160 kilometer. CWDM and DWDM SFP transceivers are also used at different wavelengths for reaching several maximum distances. Also there are Gigabit Ethernet UTP copper cable modules available.

As mentioned earlier SFP module supports speed up to 4.25 gigabit per second and an enhanced version which is called SFP+ supports more than 10 gigabit per second and SFP+ is becoming more popular on 10 gigabit ethernet.

The enhanced small form-factor pluggable (SFP+) is an improved kind of the SFP that supports data rate up to 16 gigabit per second. SFP+ supports 8 gigabit per second Fibre Channel, 10 Gigabit Ethernet and Optical Transport Network standard OTU2.

10 gigabit per second or commonly called SFP+ modules, are precisely the same sizes as regular SFPs, permitting the equipment producer to re-use present physical designs for 24 and 48 port switches and modular line cards.

The advantages of using SFP or SFP+ is, these both transceivers are typically the size of an RJ-45 ethernet port. As compared to GBIC, XENPAK or XFP modules SFP and SFP+ uses small area and standardized size of connectors. SFP sockets are commonly found in Ethernet switches, routers, firewalls and Optical Line Terminal commonly called OLT.

Recent optical SFP transceivers also support Standard digital diagnostics monitoring (DDM). This feature is commonly known as digital optical monitoring (DOM). DOM capable SFP modules give end user the ability to observer parameters of the transceiver, such as transmitted optical power, received optical power, transceiver supply voltage, laser bias current, as well as temperature of SFP in real time. This feature is commonly applied for monitoring on switches, routers and optical equipment via SNMP.

Since these SFPs are specified by a multi source agreement, which permits compatibility among different vendors. So a single SFP purchased can be used from Cisco switch to Juniper Router and from HP server to Huawei OLT. Also SFP modules are hot pluggable, so unlike other network components/cards there is no need to power off the device when inserting the SFP.

10 Gigabit Ethernet 10GBase-ZR explained

The 10GBASE SFP+ modules allow a wide variety of 10 Gigabit Ethernet connectivity options for enterprise, data center, and service provider transport applications.
BlueOptics 10G SFP+ modules are supported on a comprehensive suite of switches and routers.

The 10 Gigabit Ethernet SFP+ format has several forms and manufacturers have introduced 80 km  range ER pluggable interfaces under the name 10GBASE-ZR. This 80 km, sometimes 70Km PHY is not specified within the IEEE 802.3ae standard and manufacturers have created their own specifications based upon the 80 km PHY described in the OC-192/STM-64 SDH/SONET specifications.

SFP+10G-ZR is a multirate 10GBASE-ZR, 10GBASE-ZW, and OTU2/OTU2e module. It supports link lengths of up to about 80 kilometers on standard Single-Mode Fiber (SMF, G.652). This interface is not specified as part of the 10 Gigabit Ethernet standard and is instead built according to each manufacturer specifications. If the link is too long, there is a  risk that light following the low-order path of the next light pulse reaching the receiving side before the light following the high-order path of the current light pulse does. As a result, the receiving side will no longer be able to decode the incoming signal, resulting in interface errors (CRC, runts, invalid frames etc.), link flaps, or even no link at all.

As general features and benefits applicable to other SFP+ modules,  we can mention:

  • Smallest 10G form factor for greatest density per chassis when using SFP+ ports
  • Hot-swappable input/output device that plugs into an Ethernet SFP+ port of a switch.
  • Digital optical monitoring capability for strong diagnostic capabilities

Due to the very high transmit power, significant attenuation is needed for shorter links.  Use of ZR optics should be preceded with an optical power test of the fiber span in question to ensure a problem-free deployment. When link speed is increased, the time window between each light pulse is shorter, causing maximum supported link length to decrease. In order to improve on this, multimode fiber used today is of the type “Graded Index”. This means that the core of the fiber gradually changes the refraction index from the center out. At the center, the refraction index is higher than it is at the edge. This is because light travels faster through materials with lower refraction indexes than it does in materials with higher refraction indexes. In the end, light traveling near the edge of the fiber travels faster than light near the center, thereby compensating for the longer path the light has to travel. Single Mode fiber only has one mode or path of light, so the described phenomenon is not an issue here. The core of a single mode fiber has a very small diameter.

This optical transceiver is engineered to meet or exceed the industry’s MSA (Multi-Source Agreement) standards.

Error Analysis with Digital Diagnostics

DDM function is short for digital diagnostic monitoring according to the industry standard MSA (Multi-Source Agreement) SFF-8472 and is also known as DOM (Digital Optical Monitoring). most of the modern transceivers are with the DDM function. This technology allows the user to monitor real-time parameters of the fiber optic transceivers, like optical input/output power, temperature, laser bias current, and transceiver supply voltage.

Literally, DDM function can provide component monitoring on transceiver applications in details. However, DDM’s application is not limited to this. The SFF-8472 added DDM interface and outlined that DDM interface is an extension of the serial ID interface defined in GBIC specification, as well as the SFP MSA. DDM interface includes a system of alarm and warning flags which alert the host system when particular operating parameters are outside of a factory set normal operating. Thus, DDM interface can also enable the end user with the capabilities of fault isolation and failure prediction.

Key parameters in the performance of the fiber optic transceiver including the following:
            - Transceiver temperature
            - Transceiver supply voltage
            - Laser bias current
            - Transmit average optical power
            - Received optical modulation amplitude (OMA) or Average Optical Power

DDM can be used for fault isolation and failure prediction.

Metamorphosis of Optical Transceivers

First optical module for optical transport applications as we know today, was developed back in 1999 named 1X9. The hardware implementation was practically the fixed circuit board with a SC connector head.

Transceivers have different types and interfaces as well, which is named as “Package Form”. Package Form is the primary basis of transceiver classification and products partition. Since first type,  fiber optical module products began to develop in two aspects. One is hot-pluggable optical module, which became GBIC. The other is small, with LC head, directly solidified to the circuit board, which became SFF 2X5, or SFF 2X10.

Early days of transceiver production were unregulated, as the telecommunication components manufacturer companies were involved in its own production of transceivers. In fact at the beginning, there were one component for transmitting and another for receiving.  The market gradually become regulated and open to other manufacturers as long as the standards were respected. The MSA standards were introduced. A multi-source agreement (MSA) is an agreement between multiple manufacturers to make products which are compatible across vendors, acting as de facto standards, establishing a competitive market for interoperable products.

GBIC - is short for Gigabit Interface Converter, that has been a standard form factor for optical transceivers. Compared with 1X9, GBIC has obvious advantages, hot-pluggable feature makes GBIC can used as an independent module, users can easily maintain, update fiber optic transceivers and fault location.  Common applications include fiber channel and Gigabit Ethernet. The GBIC form factor allows manufacturers to create one type of appliance that can be used for either copper or optical applications. With the continuous development of network, GBIC module’s shortcomings also gradually appeared. The main disadvantage is its large size, resulting in a smaller density of service boards, boards can not accommodate a sufficient number of GBIC, unable to adapt to the trend of rapid development of network.

SFF Small Form Factor short, is a  small packaging technology. It is widely used in the EPON system, Ethernet Passive Optical Network. In EPON ONU side, the plain with a SFF optical module, the ONU side with the SFF optical modules the main reason is due to the system, EPON ONU Products are usually placed in the user measurement requires a fixed, rather than heat Poor pull.

SFP - The small form-factor pluggable module is hot-pluggable (like GBIC) and small (like SFF). An SFP interface on networking hardware provides the device with a modular interface that the user can easily adapt to various fiber optic and copper networking standards. SFP transceivers are commonly available in several different categories :

  • a) Fiber mode: the fundamental classification of fiber optic transceivers is the “mode type” of the fiber with which it is intended to be used. The two basic classifications of fiber mode types are: multimode and singlemode.
  • b) according to to the wavelength, there are SFP optical modules with 850nm/1310nm/1550nm/1490nm/1530nm or 1610nm. Wavelength 850nm is for SFP multi-mode, the transmission distance is below 2KM; wavelength 1310/1550nm is for single mode, the transmission distance is more than 2KM. SFP module with 1490 wavelength is single mode, generally used for long distance transmission.
  • c) According to the optical module package, fiber optic transceivers can be divided into SFP, SFP+, XFP, GBIC, X2, XENPAK, QSFP+, PON, CSFP, CFP, 1X9 and SFF. Nowadays, SFP, SFP+, XFP and QSFP+ are the popular packages and they have been widely used in many fields.
  • d) Work rate : this classification brings two distinct types — full duplex mode and half duplex mode. The full duplex mode occurs when the data transmission is transmitted by two different transmission lines. There is communication at both ends of the device and is used for both sending and receiving operations. In this type of transceiver configuration, there is typically, no time delay generated by the operation.
  • e) Connector Type : Optical fiber connectors couple and align transceivers so that light can pass through the core. Transceiver modules can be classified into different groups based on their connector types. There are four main types of fiber optic connectors used in conjunction with optical transceivers today: SC, LC, MPO, and ST.

C form-factor pluggable (CFP) is a multi-source agreement to produce a common form-factor for the transmission of high-speed digital signals. The c stands for the Latin letter C used to express the number 100 (centum), since the standard was primarily developed for 100 Gigabit Ethernet systems. The CFP was designed after the small form-factor pluggable transceiver (SFP) interface, but is significantly larger to support 100 Gbit/s. While the electrical connection of a CFP uses 10 × 10 Gbit/s lanes in each direction (RX, TX),[1] the optical connection can support both 10 × 10 Gbit/s and 4 × 25 Gbit/s variants of 100 Gbit/s interconnects. Variants: CFP, CFP2, CFP4, CFP8 and MSA(Gen1) and MSA (Gen2).

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