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Which Do You Prefer: 10GBASE-T or SFP+ DAC?

A variety of technological advancements and trends are driving the increasing need for 10 GbE in the data center. IT managers are now faced with the challenge of selecting the appropriate 10-gigabit physical media, as 10 Gigabit Ethernet (10GE) is offered in two broad categories, optical and copper, with the latter being the most commonly used means for connectivity in data centers. This article addresses the tradeoffs between the effective choices in copper connectivity 10GBase-T and SFP+ direct attach cable (DAC fiber).

What is 10GBASE-T and Why Choose It?

10GBASE-T is an IEEE 802.3an standard which supports the creation of technology that is capable of transmitting 10 Gigabit Ethernet up to 100 meters over four pairs of CAT5 balanced copper cabling system. It is an exciting technology that provides end users with cost-effective media to achieve 10Gbps data rates.

Like all BASE-T implementations, 10GBASE-T works for lengths up to 100 meters, giving IT managers a far greater level of flexibility in connecting devices in the data center. With flexibility in reach, 10GBASE-T can accommodate either top of the rack, middle of row, or end of the row network topologies. This gives IT managers the most flexibility in server placement since it will work with existing structured cabling systems. Because 10GBASE-T is backward-compatible with 1000BASE-T, it can be deployed in existing 1 GbE switch infrastructures in data centers that are cabled with CAT6 and CAT6A (or above) cabling, enabling IT to keep costs down while offering an easy migration path to 10 GbE.

What is SFP+ DAC Fiber and the Benefits of It?

SFP+ direct attach cable (DAC) is a fixed assembly that is purchased at a given length, with the SFP+ connector modules permanently attached to each end of the cable. SFP+ DAC provides high performance in 10 Gigabit Ethernet network applications, using an enhanced SFP+ connector to send 10 Gbps data through one paired transmitters and receivers over a thin twinax cable or fiber optic cable. The 10G SFP+ DAC is designed to use the same port as an optical transceiver, but compared with optical transceivers, the connector modules attached to the cable leave out the expensive optical lasers and other electronic components, thus achieving significant cost savings and power savings in short reach applications.

SFP+ DAC is a low cost alternative to traditional fiber and twisted-pair copper cabling in data center deployments. SFP+ DAC provides better cable management for high-density deployments and enhanced electrical characteristics for the most reliable signal transmission.

10GBASE-T vs 10GBASE SFP + DAC

SFP+ DAC fiber has significantly lower overall cost when you include switch, NIC and cable, however, 10GBase-T has more flexibility and can reach longer distance. For data centers, the advantages of SFP+ with DAC are a very good match for today’ s requirements and emerging trends. That’s why SFP+ DAC is being adopted rapidly as best practice for new data centers. For wiring closets, 10GBase – T will be the obvious choice once the demand for bandwidth becomes more acute and once the price and power for 10GBase-T technology comes down.

As one of the most professional optical manufacturers in China, FS solutions for 10 Gigabit Ethernet include 10G SFP+ DAC fiber, 10G SFP+ direct attach copper cable. Besides, we also provide high-quality 10G SFP transceivers, like EX-SFP-10GE-LR, SFP-10G-LR-X, SFP-10G-SR-X, etc.

Comparison Between EPON and GPON

PON is the abbreviation of passive optical network, which only uses fiber and passive components like fiber splitter and combiner. EPON （Ethernet PON) and GPON (Gigabit PON) are the most important versions of passive optical networks, widely used for Internet access, voice over Internet protocol (VoIP), and digital TV delivery in metropolitan areas. Today we are going to talk about the differences between EPON and GPON.

PON network(EPON and GPON)

Technology Comparison of EPON and GPON

EPON is based on the Ethernet standard 802.3 that can support the speed of 1.25 Gbit/s in both the downstream and upstream directions. It is well-known as the solution for the “first mile” optical access network. While GPON, based on Gigabit technology, is designated as ITU-T G.983 which can provide for 622 Mbit/s downstream and 155 Mbit/s upstream. GPON is an important approach to enable full service access network. Its requirements were set force by the Full Service Access Network (FASN) group, which was later adopted by ITU-T as the G.984.x standards–an addition to ITU-T recommendation, G.983, which details broadband PON (BPON).

As the parts of PON, they have something in common. For example, they both can be accepted as international standards, cover the same network topology methods and FTTx applications, and use WDM (wavelength-division multiplexing) with the same optical frequencies as each other with a third party wavelength; and provide triple-play, Internet Protocol TV (IPTV) and cable TV (CATV) video services.

Costs Comparison

No matter in a GPON or in an EPON, the optical line terminal (OLT), optical network unit (ONU) and optical distribution network (ODN) are the indispensable parts, which are the decisive factor of the costs of GPON and EPON deployments.

The cost of OLT and ONT is influenced by the ASIC (application specific integrated circuit) and optic module. Recently, the chipsets of GPON are mostly based on FPGA (field-programmable gate array), which is more expensive than the EPON MAC layer ASIC. On the other hand, the optic module’s price of GPON is also higher than EPON’s. When GPON reaches deployment stage, the estimated cost of a GPON OLT is 1.5 to 2 times higher than an EPON OLT, and the estimated cost of a GPON ONT will be 1.2 to 1.5 times higher than an EPON ONT.

We all know that the ODN is made up of fiber cable, cabinet, optical splitter, connector, and etc. In the case of transmitting signals to the same number of users, the cost of EPON and GPON would be the same.

Summary

Nowadays, since many experts have different opinions on EPON and GPON. Thus, there is no absolute answer to determine which is better. But one thing is clear: PON, which possesses the low cost of passive components, has made great strides driven by the growing demand for faster Internet service and more video. Also, fiber deployments will continue expanding at the expense of copper, as consumer demands for “triple-play” (video, voice and data) grow.

Optical Fiber Access Modes

Optical fiber broadband is a technology that converts electrical signals carrying data to optical signals and sends the optical signals through transparent glass fibers. The signal conversion process is completed through the optical modems installed on both ends of the optical fiber. Among various transmission media for the broadband network, optical fiber is an ideal one, which features in large transmission capacity, high transmission quality, long repeater spacing and low loss.

Optical fiber access technology provides users with high-speed bandwidth of 10 Mbps, 100 Mbps and 1000 Mbps that can be directly connected with the main crunodes of the internet. With high speed access to local area network (LAN) and high speed interconnection with internet, optical fiber access technology is applied mainly to LANs for business groups and intelligent residences. This article will introduce five common access modes of optical fiber.

Optical Fiber + Ethernet Access

Ethernet is a kind of technology for LANs and metropolitan area networks (MANs). When the optical fiber is connected with Ethernet, it is necessary to use switch, photoelectric converter and Cat5e.

Applications: residential areas and commercial buildings where generic cabling and system integration for optical fiber access are completed or easy to be implemented.

Optical Fiber + HomePNA Access

HomePNA is an industry standard for home networking over the existing coaxial cables and telephone wiring within homes. To connected optical fiber with the HomePNA, HomePNA switch (Hub) and HomePNA termination equipment (Modem) are important to connect optical fiber to the HomePNA.

Applications: residential areas and hotel buildings where generic cabling and system integration are undone or inconvenient to be done.

Optical Fiber + VDSL Access

Very-high-bit-rate digital subscriber loop (VDSL) is a technology providing data transmission over a single flat untwisted or twisted pair of copper wires and on coaxial cable. VDSL switch and VDSL termination equipment are essential to connect optical fiber with VDSL.

Applications: residential areas and hotel buildings where generic cabling and system integration are undone or inconvenient to be done.

FTTx + LAN Access

FTTx stands for fiber to the x, where x stands for home, curb, neighborhood, business, etc (as shown in the following figure). LAN refers to local area network. FTTx+LAN access aims at Gigabit Ethernet for the community, fast Ethernet for the building and 10 Mpbs Ethernet for the user.

fiber cable mix in access network

Applications: it is mainly applied to concentrated residential areas, enterprises and public institutions and universities and colleges. In FTTx+LAN, generic cabling is done in residential areas, high-class offices and student dormitories and teacher dormitories in universities and colleges.

Optical Fiber Access

Optical fiber access with transmission bandwidth from 2 Mbps to 155 Mbps is designed for enterprises and public institutions or groups who need the independent optical fiber-optic high-speed Internet. Since the bandwidth for upload and download is high, optical fiber access is suitable for such activities as remote instruction, tele-medicine and video conference.

Applications: it is applied to concentrated residential areas, communities and offices where generic cabling is done or easy to be implemented. Furthermore, it also applied to enterprises and public institutions or groups who need the independent optical fiber-optic high-speed Internet.

Optical fiber access is expanding due to the demand for broadband in consumer environment. Thus, products such as switches, photoelectric converters and transceivers used in optical fiber access are various in the market. As a professional supplier of optical communication products, Fiberstore supplies many kinds of products used in optical fiber access. Customers may choose the proper optical fiber optic access mode and optical fiber products according to their needs.

1000BASE-T – an Essential Technology in Gigabit Ethernet

Due to more and more internet users, the new applications become more various, such as Storage network, Internet data center, CAD/CAM, Multimedia and video order programs, Telemedicine, Distance learning course and other applications, all these applications need a lot of bandwidth. It is quite strict to the bandwidth of MAN and access network at the first kilometer. High speed data transmission means that the speed of a PC or server LAN ports needs to be improved to meet the new applications. At the same time, because of the rapid developments of semiconductor, 1000Base-T Gigabit Ethernet instantly become a boom.

Once we talk about 1000Base-T Gigabit Ethernet(also called IEEE 802.3ab), is a standard for Gigabit Ethernet over copper wiring. Each 1000BASE-T network segment can be a maximum length of 100 meters (330 feet) and must use category 5 cables or better (including Cat 5e and Cat 6). 10Base-T and 100Base-T are required to be mentioned, 100 Base-T, also Fast Ethernet, is simply 10Base-T running at 10 times the bit rate. Related product: 10/100/1000BASE-T Ethernet SFP. Since we know that 100Base-TX standards are compatible with 10Base-TX networks, the Fast Ethernet can make 10 Mbps and 100 Mbps bit rates on the line. Nodes with 100Mbps capabilities can communicate at 100 Mbps, and they also can communicate with slower nodes at 10 Mbps, so Fast Ethernet is the natural process of standard Ethernet, and then make the existing ethernet to be easily updated.

Fast Ethernet has been developed to 1000 Mbps (Gigabit Ethernet) on UTP cables. Gigabit Ethernet, specified as 1000Base-T, operates today over category 1 and category 5e cabling. When the ratification of 1000Base-T was done, migration of the installed base of category 5 to a higher speed Ethernet was the primary concern for network managers because they wanted to future proof their network infrastructures. While 1000Base-T Gigabit Ethernet was specified to run over category 6 cabling, most of the cabling installed that time was category 5. So the IEEE has to ensure the operation of 1000Base-T standard over the category 5 cabling systems installed according to the specifications of ANSI/TIA/EIA 568 A. The mainly goal of the IEEE 1000Base-T standard is to support the legacy category 5 cabling so that there should be no need to replace existing category 5 cabling to use 1000Base-T. According to the tack force, any link that is currently using 100Base-TX should easily support 1000Base-T. Related Product: 1000BASE-T SFP

How 1000BASE-T Gigabit Ethernet Works

As an extension of standard Ethernet technologies to gigabit-level network speeds, 1000BASE-T is normally implemented using the commonly installed category 5 cabling or enhanced category 5 cabling version of UTP cabling (for example, category 5e). Unlike using only two pairs of wires in 10BASE-T and 100BASE-T networks, 1000BASE-T uses all four cable pairs for simultaneous transmission in both directions through the use of adaptive equalization and a five-level pulse amplitude modulation (PAM-5) technique.

In the process of transmitting a 1000 Mb/s data stream over four pairs of Category 5 twisted pair cables, there are certain associated problems caused by factors as attenuation, crosstalk, and echoes arising from full-duplex transmission over single wires. To solve these problems, special filters, the PAM-5, forward error correction techniques and pulse shaping technologies are specified to make 1000BASE-T a functional and reliable networking technology. The special filters are for hybrid circuits used in full-duplex transmission over single wires. The PAM-5 provides better bandwidth utilization than binary signaling. Forward error correction techniques provide a second level of coding that helps to recover the transmitted symbols in the presence of high noise and crosstalk. Pulse shaping technologies match the spectral characteristics of the transmitted signals to those of the channel in order to maximize the signal-tonoise ratio.

Nowadays the 10 Gigabit Ethernet Alliance has been held in order to promote and accelerate the introduction of 10 Gigabit Ethernet into the fiber optic networking market. It was built by fiber optic networking industry leaders, such as 3COM, Cisco Systems, Extreme Network, Intel, Nortel Networks and other famous companies. Related product: Cisco GLC-T 1000BASE-T. Additionally, the alliance support the activities of IEEE 802.3 Ethernet committees, more force the development of the 802.3 ae (10 Gigabit Ethernet) standard, and promote interoperability among 10 Gigabit Ethernet products. The IEEE standards association unanimously approved the IEEE 802.3ae specification for 10 Gigabit Ethernet as an IEEE standard. I believe that in the near future, Ethernet will have a more comprehensive development as with continuous improvement of the system.

The Introduction to AON

1.Background
With the rapid development and globalization of the modern society, a large quantity of data needs to be transmitted, thus resulting in the explosive growth of information content. The explosive growth of information content enables people to places a higher demand on bandwidth, which is a symbol of communication content. However, the electronic bottleneck of photoelectric conversion has restricted the high-speed transmission of data, giving rise to the failure of optical communication network to meet the requirements of high-speed, large-capacity and long-haul transmission. In order to make full use of the potential bandwidth of fiber, continuously improve the transmission rate of fiber and accommodate the explosive growth of communication services, all-optical network (AON) is proposed.

2.What is AON?
All-optical network (AON) is emerging as a promising network for very high data rates, flexible switching and broadband application support. In principle, all-optical network is founded on the premise of keeping the transmission and exchange of data signals entirely in the optical domain from source to destination, thus removing the intermediate electronics to eliminate the so-called electronic bottleneck and allow arbitrary signal formats, bit-rates, and protocols to be transported. In an all-optical network, data signals are always maintained in the optical domain except when they enter or exit the network, as shown in Figure 1. It means that there is no electrical signal processing in the entire transmission, so various transmission modes (PDH, SDH, ATM, etc.) can be applied in the AON to significantly improve the utilization of network resources. Being equipped with excellent transparency, survivability, scalability and compatibility, AON can achieve the data transmission of ultra-long haul, ultra-large capacity and ultra-high speed to become the preferred choice of the future high-speed broadband network.

Figure 1: An all-optical network

3.Properties over the current optical communication network
AONs are able to arm the communication network with better manageability, flexibility and transparency. Compared with the traditional communication networks and the current optical communication networks, AONs are equipped with the following advantages that they don’t possess.
(1) AON provides huge bandwidth. Because the transmission and exchange of signals in AON entirely operate in the optical domain, AON can make the best use of the transmission capacity of fiber.
(2) AON achieves the transparent transmission. Adopting optical circuit switching to choose the routing according to wavelengths, AON is transparent to signal formats, bit-rates and modulation modes. That is to say, AON allows arbitrary signal formats, bit-rates, and protocols to be transported.
(3) AON has nice compatibility. Not only can AON be compatible with the current networks, but also AON is able to support the future broadband integrated services digital network (ISDN) as well as the network upgrade.
(4) AON possesses excellent scalability. Adding new nodes to the network has no effect on the original network architecture and node devices.
(5) AON is equipped with good reconfigurability. According to the requirements of communication capacity, AON can dynamically change the network architecture. AON is capable of recovering, building and removing the wavelength link.
(6) AON adopts lots of passive components to take place of the large photoelectric conversion equipments. Possessing simple configuration, AON is easy to maintain. At the same time, the overall exchange rate of AON can be greatly lifted to improve the reliability of network.

4.Key technologies
The key technologies applied in AONs fall into four categories: all-optical switching technology, optical cross connection (OXC) technology, optical add-drop multiplexing (OADM) technology, all-optical relay technology and optical amplifier technology.

4.1 All-optical switching technology
All-optical switching is the directly switching process which omits the OEO conversion to make full use of optical communication bandwidth. All-optical switching technology contains light-path switching technology and packet switching technology. The light-path switching can be divided into three types: space-division switching, time-division switching, wavelength/frequency-division switching. Asynchronous transfer mode (ATM), belonging to the packet switching technology, has been extensively studied.

4.2 OXC technology
OXCs are the devices applied in the optical network nodes to flexible and effectively manage the fiber transmission network by cross-connecting the optical signals. OXC technology is an important means of achieving the reliable network protection and recovery as well as automatic wiring and monitoring.

4.3 OADM technology
OADM, utilized in the optical network nodes, is able to selectively add or drop some wavelength signals as well as directly pass some wavelength signals without affecting other wavelength channel transmission. That is to say, OADM in the optical domain accomplishes the functions that SDH ADM does in time domain. OADM technology possesses transparency, thus able to deal with the signals of arbitrary formats and rates.

4.4 All-optical repeater technology
All-optical repeater technology is to directly amplify the optical signals in the optical path. Replacing the traditional OEO repeaters with the all-optical transmission repeaters, we can settle the problems of the repeater intricacy and electronic bottleneck to achieve the all-actinic signal transmission. The all-optical transmission repeaters include semi-conductor optical amplifier (SOA), Praseodymium-doped fiber amplifier (PDFA) and erbium-doped fiber amplifier (EDFA).

5.Main Components
In all-optical networks, a large quantity of optical components, which include active components and passive components. We will discuss five main components applied in all-optical networks.

5.1 Optical connectors
Optical fiber connectors are used to join optical fibers where a connect/disconnect capability is required. The connectors mechanically couple and align the cores of fibers so light can pass. Fiber Optic Connectors according to connector structure can be divided into: FC,SC, ST, LC, D4, DIN, MU, MTP, MPO and so on in various forms. The optical interface is the physical interface used to connect fiber optic cable.

5.2 WDM multiplexer/demultiplexer
In a WDM system, multiplexers at the transmitter are used to join the signals together, and demultiplexers at the receiver are utilized to split them apart. According to different wavelength patterns, WDM multiplexer/demultiplexer can be divided into CWDM multiplexer/demultiplexer and DWDM multiplexer/demultiplexer.

5.3 OADM
An optical add-drop multiplexer (OADM) is a device used in wavelength-division multiplexing systems for multiplexing and routing different channels of light into or out of asingle mode fiber (SMF). CWDM OADM is designed to optical add/drop one multiple CWDM channels into one or two fibers. DWDM OADM is designed to optical add/drop one multiple DWDM channels into one or two fibers.

5.4 Optical amplifiers
An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal.

5.5 Optical switches
An optical switch is a device used to open or close an optical circuit which enables signals in optical fibers or integrated optical circuits (IOCs) to be selectively switched from one circuit to another in telecommunication. In a network system, optical switch plays an important role in protecting the path.

6.Development prospects
All-optical network is the developing goal of the optical communication networks. To achieve the integrated all-optical network, we will experience two phases of development. The first phase is to develop the optical communication network into the all-optical transmission network. During the whole point-to-point fiber transmission process, the photoelectric conversion is not required. The second phase is to achieve the integrated all-optical network. After fulfilling the whole point-to-point transmission, lots of functions, such as signal processing, signal storing, signal exchanging, signal multiplexing/demultiplexing and so on, needs to be completed by the photonic technology. Fulfilling the functions of transmitting, exchanging and processing the end-to-end optical signals is the second developing phase—-the integrated AON.