Category: Fiber Transceivers

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There is no doubt that fiber optic cables play an integral role in telecommunication industry. Applications like data centers, local area networks, telecommunication networks, industrial Ethernet, and wireless network are all needing fiber optics to ensure smooth connectivity. Each application requires a specific cable design based on performance requirements, environmental conditions, and installation type. The common fiber optic cables like LC to LC patch cord cannot adapt to the harsh environment (e.g. moisture environment or underground deployment), thus water-resistant fiber optic cables are highly demanded on the market due to their water proof nature. Here is what you should know about the water-resistant fiber optic cable.

Overview of Water-resistant Fiber Optic Cables

Water-resistant fiber optic cable refers to the special type of fiber optic cable that are designed and specified for installations where the cable will come in contact with water or moisture, such as aerial, direct buried, or in conduit. The cables in these applications are exposed to or can be temporarily submerged in water, so they contain either a water-resistant gel-filled or gel-free (dry gel) polymer.

Generally, fiber optic cables can be divided into three types—outside plant cable (OSP), indoor/outdoor, and indoor, which are specified based on the environment and location where they are installed. With the exception of indoor cables, all cables contain water-resistant gel-filled or gel-free material to protect them from water and moisture. Before the use of gel-filled and gel-free materials, flooded core was another water-blocking method that is rarely used today (it has been replaced with gel-filled). The following image shows the gel-filled cables.

The gel is a gooey substance that must be removed when accessing and installing the cable. Gel-free cables, which are now more widely used, contain a super-absorbent polymer powder that is activated when it comes in contact with water or moisture. This blocks the water from penetrating the cable and allows for some expansion and contraction with temperature changes. Indoor cables do not contain water-resistant material since they are not typically exposed to water. Indoor (and indoor/outdoor) cables must meet additional flammability requirements dictated by local codes, such as the National Electrical Code.

Tight-Buffered & Loose Tube Cable Construction Provides Excellent Moisture Resistance

Water-resistant materials and cables are included in many industry specifications and standards. Generally, there are two basic water-resistant cable designs: Tight-buffer cables (primarily used inside buildings), Loose tube cables (used for OSP and indoor/outdoor).

It is known to all that most tight-buffered cable designs (seen in image below) are specified for indoor use, but some of them are designed with water-resistant powder and yarn, making them suitable for some indoor/outdoor applications. This tight-buffered cable utilizes an different design approach to deal with the moisture issue. Buffer materials are low-porosity plastics with excellent moisture resistance. This construction very effectively minimises the water molecule and OH-ion concentration level at the glass surface and virtually eliminates the stress corrosion phenomenon.

In loose tube cables (seen in image below), in order to prevent the water from reaching the 250Ľm coated fibers, the tubes surrounding the fibers must be filled with water-absorbent powder or gel that withstands high-moisture conditions, making them excellent for outside plant applications. This approach is especially made to waterproof the cable by filling the empty spaces in the cable with gel. The gel-filled tubes can also expand and contract with temperature changes, which makes loose-tube cable great for harsh, high-humidity environments where water or condensation can be a problem. However, gels can move, flow, and settle, leaves an uncertainty of the filled level of any particular point of a loose-tube gel-filled cable. Because loose-tube cable is typically 250 microns, you’ll need a fan-out kit to build up the individual fiber strands to 900 microns when making the transition at the entrance point from outdoor loose-tube to indoor to tight-buffered cable.

The same level of protection remains in place all along the fiber, regardless of installation conditions, environment, or time. The balance of the tight-buffered, tight bound cable designs is such that it minimizes the open spaces available in the cable structure in which water can reside. Even if an outer cable jacket is cut, or water otherwise enters the cable structure, only a very small percentage of the cross-sectional area is open to water.

by http://www.fiber-mart.com

Telecom industry embraces the prosperity of 100G optics market in 2017. With such a bright future, fiber optic market attracts a wide attention, and many vendors want a piece of the pie. The 100G optics like the CFP, QSFP28 modules and cables are varied in different standards. QSFP28 100G, along with its compact size and reliable performances, gradually becomes the mainstream form factors of the 100G optics market. QSFP28 modules come in different standards (LR4, SR4, PSM4, CWDM4), and the QSFP28 AOC and DAC cables are also available for 100G systems. Which one is ideal for your 100G network? This article attached with the detailed information of all the 100G optics, will blew your mind.

QSFP28 DAC Inside Rack: <5 m

QSFP28 passive DAC cables are launched to decrease the cost of 100G systems, which provide a cost-effective I/O solution for 100GbE connectivity within 5 m. QSFP28 to QSFP28 DACs and QSFP28 to 4x SFP28 DACs are the two common types of the QSFP28 DAC cables. QSFP28 to QSFP28 direct attach cable is usually used inside racks with QSFP28 connectors terminated on each end. QSFP28 breakout DACs can achieve 25G to 100G transmission with a QSFP28 connector on one end and 4 SFP28 connectors on the other end. If your 100GbE deployment is within 5m intra racks, the QSFP28 DAC is ideal for you.

QSFP28 AOC: Up to 100 m

The QSFP28 AOC is a cost-efficient, four-channel optical transceiver that conforms to the QSFP28 multi-source agreement. It is capable of delivering 100-Gbps data rates over four lanes of 25 Gbps with a reach of up to 100 m, maximum. Just as the QSFP28 DAC, QSFP28 AOC cable also comes in two types—QSFP28 to QSFP28 AOC and QSFP28 to 4SFP28 AOC. The former one is best fit for 3-20 m, and QSFP28 breakout can support a link length of up to 100 m. The QSFP28 AOC supports InfiniBand EDR and 100 Gigabit Ethernet (100GBase-SR4) transmission speeds and is best for close-range, high-speed transmission in data center networks, such as between servers and server racks.

QSFP28 SR4 Close Range: 5-100 m

For 100GbE cabling with multimode fiber between switches, QSFP28 SR4 with 12-fiber OM4 MTP fiber cable is the perfect choice. It can support reaches up to 100 m over OM4. The 100Gbase-SR4 QSFP28 module achieves four lanes of 25G dual way transmission over eight fibers. QSFP28 SR4 module is compliant with 100GBASE-SR4 standard certificated by IEEE. It is the firstly published 100G standard to support short distance over multimode fibers. Many vendors offer the compatible QSFP28 SR4 optics with good quality and high reliability. fiber-mart.COM is one of the best that can provide the test-assured OEM optics with great customer feedback. All the products included in the below chart are provided at fiber-mart.COM.

QSFP PSM4 Between Switches: 100 m-500 m

For 100G connectivity, if the reaches are beyond 100m but less than 500m, you can use the QSFP PSM4. Unlike the QSFP28 SR4 optics (by IEEE), PSM4 standard is published by MSA. 100G PSM4 QSFP28 is designed to support a transmission distance up to 500 m over MPOI single-mode multi-fibers.

QSFP CWDM4 Mid-Reach: 500 m-2 km

Reaches less than 2 km are usually called mid-reaches. QSFP28 CWDM4 is the module designed to meet the mid-reach requirements. MSA published 100Gbase-CWDM4 standard for QSFP28 over single-mode up to 2 km over through duplex LC interface. It uses WDM technologies like 100Gbase-LR4. But the transmission distance is shorter and the cost is much lower.

QSFP28 LR4 Long Span: d10 km

For long distance transmission between two buildings, the IEEE standard 100Gbase-LR4 is being used in QSFP28 form factor which is known as QSFP-100G-LR4 module. Unlike QSFP-100G-SR4 modules, QSFP-100G-LR4 uses the WDM technologies for four 25G lanes transmission. The four 25G optical signals are being transmitted over four different wavelengths. It has a duplex LC interface for 100G dual-way transmission. 100Gbase-LR4 QSFP28 can support transmission up to 10 km over single-mode fiber. But one problem is that the cost of QSFP28 LR4 is very high now. What’s worse, you would need the EDFA to offiber-martet the link loss.

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The demand for better network throughput and performance has never ceased. Instead, it has become more and more vigorous. The server consolidation, virtualization, as well as networking-service performance improvements, all these have pushed the necessity for dense 40GbE switch connections in data centers.

But when migrating to 40GbE from10GbE, some companies or organizations are challenged by two main factors in re-configuring the physical layer of the network: firstly, the possible reduced reach of the OM3/OM4 multi-mode optics from 10GBASE-SR (300/400 m) to 40GBASE-SR4 (100/150m), and secondly, the need to upgrade the existing fiber optic cabling plant so as to support the IEEE-defined 40GBASE-SR4 parallel optics. In order to avoid these questions, SMF&MMF 40G QSFP+ transceiver is brought to the market.

SMF&MMF 40G QSFP+ Transceiver Definition

It’s know that a fiber optic transceiver may either operate on single-mode fiber (SMF) or multi-mode fiber (MMF). However, this SMF&MMF 40G QSFP+ transceiver is able to communicate with both SMF and MMF, without the need for any software/hardware changes to the transceiver module or any additional hardware in the network. It has 4 channels (1270, 1290,1310, and 1330nm) of 10G multiplexed inside the module to transmit and receive an aggregate 40G signal over 2 strands of fiber with a duplex LC connector.

Based on IEEE defined 40GBASE-LR4 specifications, this supports distances up to 150m over OM3 or OM4 MMF and up to 500m over SMF. Certainly, different fiber optic equipment vendors may have different specifications.

SMF&MMF 40G QSFP+ Transceiver Advantages

SMF&MMF 40G QSFP+ transceiver is designed for seamless migrations from existing 10GbE to 40GbE networking without modification or expansion of the fiber network. It addresses several challenges faced by today’s data centers and the passages highlight the advantages of this transceiver.

No Redesign or Expansion of Fiber Network

Other short-reach 40G QSFP+ transceiver types, such as MMF 40GBASE-SR4 transceivers (100m over OM3 MMF), utilize four independent 10G transmitters and receivers for an aggregate 40G link. These 40GBASE-SR4 transceivers (eg. JG325B) use a MPO-12 connector and require 8-fiber parallel OM3 or OM4. As a result, customers installing MTP/MPO fiber systems may need to deploy new fiber while upgrading from 10G to 40G. However, SMF&MMF 40G QSFP+ transceiver uses duplex LC connector, which is consistent with the existing 10G connections. It works on existing OM3 and OM4 MMF infrastructure which is widely installed and used for 10GbE networks, thus free from redesign or expansion of the fiber network.

Increase in the Number of 40G Links

The existing MMF 40GbE solutions use of 8 fibers for a 40G link, and customers have to add additional fiber if they want to increase the number of 40G links. But if you deploy SMF&MMF 40G QSFP+ transceiver, the number of 40G links is 4our times of that existing MMF 40GbE solutions without any changes to their fiber infrastructure. During this link increase, the network scale and performance are also expanded.

A Cost-effective Solution for SMF Infrastructure

Limited in the distance reach that multi-mode transceivers can support, the migration from 10G to 40G, to 100G, or even 400G would become simpler with SMF. But single-mode transceivers typically cost up to 4 times more compared to multi-mode transceivers. Since SMF&MMF QSFP+ transceiver interoperates with QSFP-LR4 and QSFP-LR4L optics, it’s a cost effective solution for SM fiber infrastructure for distances up to 500m. And customers can deploy mixed connections without fiber concerns.

Simplification in Infrastructure Deployment

SMF&MMF QSFP+ transceiver boasts of the unique characteristic of working through both SMF and MMF without any requirement for additional fiber. Customers can consolidate their optics and use SMF&MMF QSFP+ transceiver in their network without concern about the fiber type, which makes the full use of existing cabling infrastructure, leading to the reduced equipment cost and simplification of deployment.

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Since Ethernet technology came into people’s use in 1970s, Gigabit Ethernet (GbE) has long deminated the local area network (LAN) applications. But when to connect servers to storage area networks (SANs) and network attached storage (NAS) or for server-to-server connections, GbE seems to be not sufficient enough. In such a case, Ethernet has developed the later technology standard as newer, higher performing iteration—10GbE.

The Institute of Electrical and Electronics Engineers (IEEE) 802.3 working group has published several standards regarding 10GbE, including 802.3ae-2002 (fiber -SR, -LR, -ER), 802.3ak-2004 (CX4 copper twin-ax InfiniBand type cable), etc. Among these standard interfaces, 10GBASE-SR is the most-widely used type, like Cisco SFP-10G-SR and Cisco SFP-10G-SR-S. With 10Gigabit connectivity becoming widely available, 10GbE technology has emerged as the connection choice for many companies to grow their networks and support new applications and traffic types. Behind the 10GbE, there are three main advantages which explain why users choose it today.

Data Center Network Simplification

While Fibre Channel and InfiniBand are specialized technologies that can connect servers and storage, they can’t extend beyond the data center. However, a single 10GbE network and a single switch can support the LAN, server-to-server communications, and can connect to the wide-area network. Ethernet and IP network technology are familiar to network designers, so replacing multiple networks with a single 10GbE network avoids complex staff training. And by consolidating multiple gigabit ports into a single 10gigabit connection, 10GbE simplifies the network infrastructure while providing greater bandwidth.

Traffic Prioritization and Control

A major advantage of 10GbE is that separate networks for SANs, server-to-server communication and the LAN can be replaced with a single 10GbE network. While 10Gb links may have sufficient bandwidth to carry all three types of data, bursts of traffic can overwhelm a switch or endpoint.

SAN performance is extremely sensitive to delay. Slowing down access to storage has an impact on server and application performance. Server-to-server traffic also suffers from delays, while LAN traffic is less sensitive. There must be a mechanism to allocate priority to critical traffic while lower-priority data waits until the link is available.

Existing Ethernet protocols do not provide the controls needed. A receiving node can send an 802.3x PAUSE command to stop the flow of packets, but PAUSE stops all packets. 802.1p was developed in the 1990s to provide a method to classify packets into one of eight priority levels. However, it did not include a mechanism to pause individual levels. The IEEE is now developing 802.1Qbb Priority-based Flow Control (PFC) to provide a way to stop the flow of low-priority packets while permitting high-priority data to flow.

A bandwidth allocation mechanism is also required. 802.1Qaz Enhanced Transmission Selection (ETS) provides a way to group one or more 802.1p priorities into a priority group. All of the priority levels within a group should require the same level of service. Each priority group is then assigned a percentage allocation of the link. One special priority group is never limited and can override all other allocations and consume the entire bandwidth of the link. During periods when high-priority groups are not using their allocated bandwidth, lower-priority groups are allowed to use the available bandwidth.

Congestion control

802.1Qbb and 802.1Qaz by themselves don’t solve the packet loss problem. They can pause low-priority traffic on a link, but they don’t prevent congestion when a switch or an end node is being overwhelmed by high-priority packets from two or more links. There must be a way for receiving nodes to notify sending nodes to slow their rate of transmission.

IEEE 802.1Qau provides such a mechanism. When a receiving node detects that it is nearing the point where it will begin discarding incoming packets, it sends a message to all nodes currently sending to it. Sending nodes slow their transmission rate. Then, when congestion is cleared, the node sends a message informing senders to resume their full rate.

10GbE in Data Centers

For many institutions, especially those that utilize automated trading, uptime and response time is critical. Longer delays than a second can be exceedingly costly. With servers now being able to transmit bandwidth and network downtime, today’s data centers of some companies need extended bandwidth. 10GbE is an ideal technology to move large amounts of data quickly. The bandwidth it provides in conjunction with server consolidation is highly advantageous for Web caching, real-time application response, parallel processing and storage.

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New sophisticated networking services, coupled with the increase of Internet users push the Internet traffic to an even higher point, driving the need for increased bandwidth consequently. One Ethernet technology—10 Gigabit Ethernet (GbE) is adequate for such bandwidth demand, and has become widely available due to the competitive price and performance, as well as its simplified cabling structure.

Several cable and interconnect solutions are available for 10GbE, the choice of which depends on the maximum interconnect distance, power budget and heat consumption, signal latency, network reliability, component adaptability to future requirements, cost. Here cost includes more than what we call the equipment interface and cable cost, but more often the labor cost. Thus, choosing a 10GbE interconnect solution requires careful evaluation of each option against the specific applications. This text aims to introduce two main 10GbE interconnect solutions: fiber optics and copper.

Fiber Optics Solution

Fiber optic cables include single-mode fiber (SMF) and multi-mode fiber (MMF). MMF is larger in diameter than that of single-mode, thus portions of the light beam follow different paths as they bounce back and forth between the walls of the fiber, leading to the possible distorted signal when reach the other end of the cable. The amount of distortion increases with the length of the cable. The light beam follows a single path through thinner single-mode cable, so the amount of distortion is much lower.

The typical 10GBASE port type that uses MMF is 10GBASE-SR which uses 850nm lasers. When used with OM3 MMF, 10GBASE-SR can support 300m-connection distances, and when with OM4 MMF, 400m link length is possible through 10GBASE-SR SFP+ transceiver.

10GBASE-LR (eg. E10GSFPLR), 10GBASE-ER and 10GBASE-ZR are all specified to work via SMF. SMF can carry signals up to 80km, so it is more often used in wide-area networks. But since SMF requires a more expensive laser light source than MMF does, SMF is replaced by MMF when the required connection distance is not so long.

Copper Solution

10GBASE-CX4, SFP+ Direct Attach (DAC) and 10GBASE-T are all specified to operate through copper medium.

10GBASE-CX4

Being the first 10GbE copper solution standardized by the IEEE as 802.3ak in 2002, 10GBase-CX4 uses four cables, each carrying 2.5gigabits of data. It is specified to work up to a distance of 15m. Although 10GBase-CX4 provides an extremely cost-effective method to connect equipment within that 15m-distance, its bulky weight and big size of the CX4 connector prohibited higher switch densities required for large scale deployment. Besides, large diameter cables are purchased in fixed lengths, causing problems in managing cable slack. What’s more, the space isn’t sufficient enough to handle these large cables.

SFP+ DAC

SFP+ Direct Attach Cable (DAC), or called 10GSFP+Cu, is a copper 10GBASE twin-axial cable, connected directly into an SFP+ housing. It comes in either an active or passive twin-axial cable assembly. This solution provides a low-cost and low energy-consuming interconnect with a flexible cabling length, typically 1 to 7m (passive versions) or up to 15m (active versions) in length. Below is the SFP+ to SFP+ passive copper cable assembly with 1m length, 487655-B21, a HP compatible 10GbE cabling product.

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A continuous stream of manufacturing process improvements and product innovations has given fiber optical system several advantages, like longer distance reach, larger data-carrying capacity, greater bandwidth and lower power consumption. Among these fiber optical product innovations, hot-pluggable transceiver modules should come to the central point with their unique designs. They have been constantly designed, and finally been reinvented as hot-pluggable modules along with the optical technological advances. These small, hot-pluggable serve as the key components in accommodating the demands of higher port density and more networking flexibility.

Transceiver modules come into various types: SFP (small form-factor pluggable), SFP+ (small form-factor pluggable plus), QSFP+ (quad small form-factor pluggable plus), etc. This article mainly introduces SFP transceiver modules which are widely applied in Gigabit Ethernet (GbE) applications, with the focus on several 1000BASE-X interface types, including 1000BASE-SX, 1000BASE-LX, 1000BASE-EX, and 1000BASE-BX10-D/U.

Features and Benefits

1000BASE-X SFP modules provide a wide range of form factor options for enterprise and service provider needs. They are designed with the following features and benefits:

Hot swappable to maximize uptime and simplify serviceability;

Flexibility of media and interface choice on a port-by-port basis, so you can “pay as you populate”;

Sophisticated design for enhanced reliability;

Supports digital optical monitoring (DOM) function;

1000BASE-X SFP Interface Types

1000BASE-SX SFP

1000BASE-SX SFP, compatible with the IEEE 802.3z 1000BASE-SX standard, operates on legacy 50Ľm multi-mode fiber (MMF) links up to 550m and on 62.5Ľm Fiber Distributed Data Interface (FDDI)-grade MMfiber-mart up to 220m. Take DEM-311GT for example, Fiberstore compatible D-Link 1000BASE-SX SFP is able to realize 550m link length through OM2 MMF with duplex LC.

1000BASE-LX SFP

1000BASE-LX SFP, compatible with the IEEE 802.3z 1000BASE-LX standard, is specified to support link length of up to 10km on standard single-mode fiber (SMF), to 550m on MMfiber-mart. When used over legacy MMF, the transmitter should be coupled through a mode conditioning patch cable. The laser is launched at a precise offiber-martet from the center of the fiber which causes it to spread across the diameter of the fiber core, reducing the effect known as differential mode delay which occurs when the laser couples onto only a small number of available modes in MMF.

1000BASE-EX SFP

1000BASE-EX, sometimes referred to as LH, is a non-standard but industry accepted standard which works on standard SMF with fiber link spans up to 40km in length. For back-to-back connectivity, a 5-dB inline optical attenuator should be inserted between the fiber optic cable and the receiving port on the SFP at each end of the link. 1000BASE-EX SFPs (eg. GLC-EX-SMD) run on 1310nm wavelength lasers, and achieves 40km link length.

1000BASE-BX10-D/U SFP

The 1000BASE-BX-D and 1000BASE-BX-U SFPs, compatible with the IEEE 802.3ah 1000BASE-BX10-D and 1000BASE-BX10-U standards, operate on a single strand of standard SMF (figure shown below). A 1000BASE-BX10-D device is always connected to a 1000BASE-BX10-U device by a single strand of standard SMF with an operating transmission distance up to 10km.

The communication over a single strand of fiber is accomplished by separating the transmission wavelength of the two devices (figure shown above): 1000BASE-BX10-D transmits a 1490nm channel and receives a 1310nm signal, whereas 1000BASE-BX10-U transmits at a 1310-nm wavelength and receives a 1490-nm signal. In this figure, the wavelength-division multiplexing (WDM) splitter is integrated into the SFP to split the 1310nm and 1490nm light paths.