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Generations of Fibre Channel and their Differences

Fibre Channel (usually abbreviated as FC) is a technology used for high-speed data transfer. Fibre channels finds its main use in storage area networks (SAN). FC is used to transfer data between computer storages and computer systems. Fibre channel can provide data transfer speeds of up to 128 Gbps.

FC is a widely used technology, almost all of the high-end servers and storages have interfaces to support FC. Another variant of fibre channel is Fiber Channel over Ethernet (FCoE). FCoE uses ethernet network as a transport medium, FC packets are encapsulated over the ethernet network, thus providing data transfer speeds of 10 Gbps or higher.

In this article, we will look in to the evolution of fibre channel technology, starting from its 1st generation and discussing the subsequent advancements in this technology. In the end, we will draw a comparison of the different generations of fibre channel. A high-level evolution of fibre channel technology is given in table 1.

Sr.#

Name

Year

1

1G FC

1997

2

2G FC

2001

3

4G FC

2004

4

8G FC

2005

5

10G FC

2008

6

16G FC

2011

7

32G FC

2016

8

128G FC

2016

Table 1: Different Versions of Fiber Channel

Fibre channel was standardized by the T11 Technical Committee of the International Committee for Information Technology Standards (INCITS). A close look at table 1 shows that FC started with a 1 Gbps data transfer speed and the speeds are doubled with every generation. Currently, 128G FC is also available.  

1G Fibre Channel

1G FC was the first standardized version of fibre channel technology. Introduced in the year 1997. 1G FC provides a throughput of 200 Mega Bytes per Second (MBps, not to be confused with Mega Bits per second, Mbps). 1G FC instantly gained popularity due to its application in storage area networks. 1G fibre channel remained in use till late mid-2000s.

2G Fibre Channel

2G FC was the next step in the evolution of fibre channel technology. The work on its development started soon after the release of 1G fibre channel and it was released as an industry standard in the year 2001 by T11 Committee. 2G FC doubled the speed offered by 1G FC. 2G FC has a throughput of 400 MBps in full duplex mode. 2G fibre channel was also widely used in the storage area networks.

4G Fibre Channel

In the year 2004, the next version in the fibre channel technology series was made available to the manufacturers worldwide. 4G fibre channel also doubled the service level parameters as compared to 2G FC. 800 MBps of full duplex throughput can be achieved in 4G fibre channel. 4G fibre channel gained so much popularity that it is still in use in some older SAN storages and servers.

8G Fibre Channel

8G fibre channel was released in quick succession to its predecessor. It was standardized and made available in the year 2005, just one year after the release of 4G fibre channel. These two fibre channel versions are the most popular FC versions available in the market. 8G fibre channel is also still in use and the interface cards are still available for 8G FC. 1600 MBps full duplex throughput is available in 8G fibre channel.

10G Fibre Channel

10G fibre channel version was developed for FCoE to make full use of the 10 Gbps ethernet networks. 10G FC is rarely used apart from its application in conjunction with FCoE. FCoE transmits FC data using ethernet frames.

16G Fibre Channel

The next step that followed in the line of fibre channel generations was 16G fibre channel. It was released in 2011 by the T11 Committee. 16G FC followed the “double-throughput” precedence set by the first four versions of fibre channel. Its throughput is 3200 MBps. Although, 16G FC was released in 2011, but it gained in popularity recently. Now a days, 16G fibre channel comes as a standard option in almost all of the latest SAN storages and servers. After the release of 10G fibre channel, the industry decided to change the naming convention of fibre channel versions. With the release of 16G FC, it was decided to discard the speed-based naming and adopt generation-based naming. 16G fibre channel was named 5th generation fibre channel. The first four versions being the 1G, 2G, 4G and 8G fibre channels.

32G Fibre Channel & 128G Fibre Channel

Sixth generation of fibre channel technology consists of two versions, 32G FC and 128G FC. Both of these versions were released in 2016. The sixth generation of fibre channel provides incredible increase in the throughputs. 32G FC is capable of providing 6400 MBps of throughput whereas the 128G FC is capable of providing 25600 MBps of throughput. The sixth generation fibre channel technology was designed to make full use of the Solid State Drive storage. SSD storage is a diskless storage providing faster data transfer rates as compared to the traditional hard disk drives. The sixth generation fibre channel also introduced new features for better security and lesser power consumption as compared to its predecessors.

Comparison

Fibre channel technology has seen a great evolution in speed, security and power consumption. It has kept its pace with the changing technologies and stayed in the market for so long. The popularity of fibre channel is gaining day by day. Almost all of the enterprise grade servers and storage devices come with pre-installed fibre channel adapters. The pace with which this technology is advancing, we see a long-term prospect for its continued usage in the information technology industry.

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What is a 25G SFP28 Optical Transceiver?

The 25G Ethernet solution is a solution standardized and developed by IEEE 802.3 task force P802.3by. This solution is mainly concentrated for use in datacenter environment. The 25 G Ethernet consortium has been formed in July 2014 to support the deployment of single lane 25GB/s solutions and dual-lane 50GB/s Ethernet solutions. The 25GB Ethernet consortium has been finished since September 2015. In November 2015 the 802.3 task force has been formed to develop the single-lane 25 GB/s Ethernet solution and on June 30 the IEEE 802.3by standard has been approved by the IEEE-SA Standards board.

The IEEE 802.3by standard defines the technologies below:

  • A single lane 25 GB/s 25GBASE-KR PHY for printed circuit backplanes. PHY is a type of chip which is an abbreviation for the physical layer of the OSI model
  • A single-lane 25 GB/s 25GBASE-CR-S PHY for 3 meters twin-ax cables (in-rack)
  • A single-lane 25 GB/s 25GBASE-CR-L PHY for 5 meters twin-ax cables (inter rack)
  • A single-lane 25 GB/s 25GBASE-SR PHY for 100 m OM4 or 70 m OM3 Multi-mode optical fiber

The 25GB Ethernet equipment has been available on the market for purchase since June 2016 and it uses the SFP28 and QSFP28 Optical transceivers. Also, direct attach SFP28 to SFP28 cables are available with fixed lengths of 1, 2, 3 and 5 meters. These are manufactured by various manufacturers. Also, lately have been announced the optical transceivers which will support 1310nm “LR” optics which will be able to reach from 2 kilometers up to 10 kilometers over a two strands of Single-mode fibers.

There are several factors to successfully create a fully functioning 25GB Ethernet Network. Optical transceivers and Direct Attach Cables that would support the 25GB and 50GB Ethernet are a must and at the end of the connection the NIC cards which have to support these solutions will guarantee the maximum performance. The deployment of 25GB Ethernet solution in Datacenters will definitely boost the whole core network, storage network and cloud computing network, thus providing the customers with greater bandwidth and stability utilizing the 10GB Ethernet solutions.

The SFP28 optical transceiver, which is a transceiver based on the widely popular SFP+ Form-Factor, introduces a new generation of high-density 25 GB/s Ethernet applications for Datacenters and Enterprise companies. It provides a conventional and cost-effective upgrade.

CBO BlueOptics© offers two models of SFP28 with Duplex connector:

  • BO27Q13610D 25GBASE-LR, SFP28 Optical transceiver
  • BO27Q856S1D 25GBASE-SR, SFP28 Optical transceiver

BlueOptics© SFP28 25GBASE-LR, 1310nm, 10KM, Optical Fiber Transceiver, DDM/DOM

BlueOptics© SFP28 25GBASE-SR, 850nm, 100M, Optical Fiber Transceiver, DDM/DOM

The CBO BlueOptics© BO27Q13610D 25GBASE-LR, SFP28  is a superior performance optical transceiver capable for long range distances up to 10 kilometers on Single-mode fibers and speeds up to 25.78 Gigabits per second. It features the Digital Diagnostic Monitoring feature and it can be used in 1310 optical window. This transceiver fulfills the 802.3by standard and even exceeds the Multiple Source Agreements (MSA). It features the Digital Diagnostic Monitoring feature for real-time parameter monitoring and the option for alarms if the high level threshold is exceeded.

The CBO BlueOptics© BO27Q856S1D 25GBASE-SR, SFP28 is a short range optical transceiver capable for reaching distances up to 100 meters over Multi-mode fibers. Unlike the previous model, this transceiver can be used in the 850 nm optical window, however it provides the same speed like the LR (long range) model with up to 25.78 Gigabits per second. The Digital Diagnostic Monitoring feature comes standard and it has up to 3.000.000 MTBF working hours.

Both models come with 5 year warranty and a lifetime support.

What Is a Mode Conditioning Patch Cord

Transceivers modules that are used in gigabit Ethernet 1000base-LX launch only single mode 1030nm wavelength signals. This creates a problem if present network operates on multimode cables.

When a single mode signal is launched into multimode fiber a phenomenon called Differential Mode Delay (DMD) can create multiple signals within the multimode fibers. This effect can confuse the receiver and produce the errors. These multiple signals, caused by DMD, severely limit the cable distance lengths for operating Gigabit Ethernet. A mode conditioning patch cord eliminates these multiple signals by letting the single-mode launch to be offset away from center of the multimode fiber. This offset point creates a launch that is similar to typical multimode LED launch and the resulting multiple signals allowing the use of 1000base-LX over existing multimode cable system.

Mode conditioning patch cords are necessary where Gigabit 1000 Base-LX switches and routers are installed into present multimode cable plants. These specified cords help avoid Differential Mode Delay (DMD) effects that can happen when long wave transceiver modules operate at both single-mode and multimode fibers. The mode conditioning patch cord lets the single-mode transceiver to generate a launch similar to a typical multimode launch.

Mode conditioners are constructed in the form of a simple duplex patch cord, so they can easily be mounted in a system without the need for extra components or hardware. Their length can vary from one meter and up, to support almost any network topography.

The conditioned side of mode condoning cable comprises of a yellow (single-mode) fiber which has been spliced to an orange (multimode) fiber in an offset mode, with a specific core placement and angle. On the other hand, the non-conditioned side of cable consists of one piece of orange (multimode) cable. The yellow leg (single-mode) of the cable must be connected to the transmit side, and the orange leg (multimode) had to be connected to the receive side of the equipment.

Since the optical SPF transceivers used in 1000 base LX uses LC connectors, the produced mode conditioning cord will have LC connector at one side. Depending upon the production of cable the other side of the cable could be SC connector, FC connector, MTRJ connector or the other side could be same as LC connector. Not to forget that there would be also an insertion loss from 0.2dB to 0.5dB in mode conditioning cable. Mode conditioning cables are available for both 62.5/125µm and 50/125µm multimode fibers.

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What is an Optical Add/Drop Multiplexer - OADM?

Introduction

Fiber optic communication networks are becoming increasingly popular day by day. All of the corporate networks as well as service provider networks make use of the fiber optic communication technology to efficiently serve their end users. Fiber optic communications are also making inroads into the houses of the end users. With the advent of FTT-X networks, the usage of fiber optic cables has increased exponentially. It is not possible to have a dedicated fiber cable pair for each link as it would take a lot of space and the links would still be under-utilized.

To make fiber optic communications more effective and efficient, engineers developed a technique called multiplexing which allowed different signals to travel on a single fiber optic cable without interference. Multiplexing is widely used in its various forms across all the communication methods that are currently in use today.

OADM

An optical add-drop multiplexer (OADM) is a critical device that is used in the wavelength-division multiplexing systems for multiplexing and routing different channels of light into or out of a single mode fiber (SMF).It is one of the fundamental constructional blocks of the modern day telecommunications networks.

Components of OADM

Traditionally, an OADM has three major components which are responsible to carry out the task assigned to an OADM. These three components are given below:

  • Optical Demultiplexer
    • An Optical Demultiplexer separates the multiple of wavelengths in a fiber and directs them to many fibers
  • Optical Multiplexer
    • The optical multiplexer is used to couple two or more wavelengths into the same fiber
  • A set of ports for adding and dropping signals

Types of OADM

There are two main types of OADM that are widely used in communication networks, namely, Fixed OADM (FOADM) and Reconfigurable OADM (ROADM). An OADM with remotely reconfigurable optical switches in the middle stage is called a reconfigurable OADM (ROADM). Ones without this feature are known as fixed OADMs. Fixed OAMDs are used to drop or add data singles on dedicated channels, and reconfigurable OADMs have the ability to electronically alter the selected channel routing through the optical network. While the term OADM applies to both types, it is often used interchangeably with ROADM.

Fixed Optical Add-Drop Multiplexer (FOADM)

FOADMs use fixed filters that add/drop a selected wavelength and pass the rest of the wavelengths through the node. Static wavelength-filtering technology eliminates the cost and attenuation to demultiplex all DWDM signals in a signal path. The solution is called FOADM because the wavelengths added and dropped are fixed at the time of add/drop filter installation on the optical path through a node.

Reconfigurable Optical Add-Drop Multiplexers (ROADM)

Reconfigurable Optical Add Drop Multiplexers (ROADMs) are used to provide flexibility in rerouting optical streams, bypassing faulty connections, allowing minimal service disruption and the ability to adapt or upgrade the optical network to different WDM technologies my electronically configuring the OADM to achieve the required functionality.

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Serial Attached SCSI (SAS), MiniSAS (SFF-8088) and MiniSAS HD (SFF-8644) Comparison

Serial Attached SCSI (SAS) is a communication protocol used for communication between computer storage devices such as hard-disk drives. SCSI stands for Small Computer System Interface. SAS protocol is developed by T10 technical committee of the International Committee for Information Technology Standards (INCITS).

SAS-1, the first version of SAS was initially introduced in the year 2004. Before the introduction of SAS, SATA hard-drives were more popular in computer systems. SATA is still being used in personal computers but it has been replaced by SAS almost completely in the enterprise grade servers and storage systems.

SAS offers higher data transfer rates, SAS-1 (y. 2004) provided up to 3 Gbps data transfer, SAS-2 (y. 2009) provided up to 6 Gbps and SAS-3 (y. 2013) provides up to 12 Gbps data transfer rate. SAS-4 is under development and is expected to be released in 2017. SAS-4 will support data transfer rate of 22.5 Gbps. Table 1 summarizes the different versions of SAS.

S.#

Version

Year

Data Transfer Rate

1

SAS-1

2004

3 Gbps

2

SAS-2

2009

6 Gbps

3

SAS-3

2013

12 Gbps

4

SAS-4

Exp. 2017

22.5 Gbps

Table 1: SAS Versions

There are several connectors and cables available in the market for SAS connections, a few of the connectors which are commonly used are SFF-8087, SFF-8088, SFF-8643 and SFF-8644 etc. SFF-8087 and SFF-8088 support up to 6 Gbps (SAS-2) and SFF-8643 and SFF-8644 support 12 Gbps SAS (SAS-3) connections.

The other classification of connectors is internal and external SAS connectors, internal connectors are used for internally connecting the different hard drives to the computer system, whereas, the external connectors are used to connect hard drives or storage systems of different computer systems. For example, the connection of a server’s SAS hard drive with the mother board is established using the internal connectors whereas the connection between the SAN Storage and a server’s SAS hard drive is established using the external connectors.

Of the above mentioned connectors, SFF-8087 and SFF-8643 are internal connectors and SFF-8088 and SFF-8644 are external connectors.

SAS Direct Attach Cables are also available to connect various storage devices. A sample of the available SAS cables is shown in figure 1.


Figure 1: SAS Cables

Different types of cables which are available at CBO are:

  • MiniSAS Hybrid Cable, SFF-8088 to SFF-8644
  • MiniSAS Cable, SFF-8088 to SFF-8088
  • MiniSAS HD Cable, SFF-8644 to SFF-8644, 12G

SAS cables are available in various lengths starting from 1 meter up to 10 meters. Choice of the length is dependent on the physical distance between the two connecting systems. SAS cables are twinax copper cables, they provide convenience and an efficient way to achieve faster data transfer rates within small distances inside a data center.

The SFF-8088 is 26 pin connector whereas SFF-8644 is a 36 pin connector. Hybrid cables are used for backward compatibility between SAS-2 and SAS-3 supported computer systems. A SAS-3 cable i.e., SFF-8644 to SFF-8644 is also called MiniSAS HD Cable.

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