Category: Fiber Transceivers

Optical transceivers, Active Optic Cables, data center switches, and cable management in data centers.

The Difference Between Loose Tube Fiber and Tight Buffer Fiber

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

Tight-buffered cables oftenn are used for intra-building, risers, general building and plenum applications. Tight buffer fiber contains a thick coating of a plastic-type material which is applied directly to the outside of each individual fiber. Loose tube fiber optic cable is typically used for outside-plant installation in aerial, duct and direct-buried applications. Loose tube fiber contains multiple strands of fiber in a single jacket. Since the fibers are “loose” inside the jacket, outside forces are less likely to reach the fibers. This makes it the more durable option of the two.
Loose Tube Cable
Loose-tube fiber generally consists of 12 strand of fiber, but can range anywher as low as 6, all the way up to 244 strands. Loose tube cables can be either dielectric or optionally armored. The modular buffer-tube design permits easy drop-off groups of fibers at intermediate points, without interfering with other protected buffer tubes being routed to other locations. The loose tube design also helps in the identification and administration of fibers in the system.
In a loose tube cable design, color-coded plastic buffer tubes house and protect optical fibers. An optional gel filling compound impedes water penetration. Excess fiber length (relative to buffer tube length) insulates fibers from stresses of installation and environmental loading. Buffer tubes are stranded around a dielectric or steel central member, which serves as an anti-buckling element.
The cable core, typically uses aramid yarn, as the primary tensile strength member. The outer polyethylene jacket is extruded over the core. If armoring is required, a corrugated steel tape is formed around a single jacketed cable with an additional jacket extruded over the armor.
Tight-Buffered Cable
Single fiber tight buffered cables are used as pigtails, optical patch cord or fiber jumpers to terminate loose tube cables directly into opto-electronic transmitters, receivers and other active and passive components. Multi fiber tight buffered cables also are available and are used primarily for alternative routing and handling flexibility and ease within buildings. With tight buffered cable designs, the buffering material is in direct contact with the fiber. This design is suited for “jumper cables” which connect outside plant cables to terminal equipment, and also for linking various devices in a premises network.
The tight-buffered design provides a rugged cable structure to protect individual fibers during handling, routing and connectorization. Yarn strength members keep the tensile load away from the fiber.
As with loose-tube cables, optical specifications for tight-buffered cables also should include the maximum performance of all fibers over the operating temperature range and life of the cable. Averages should not be acceptable.

 

Planar Lightwave Circuit (PLC) Based Optic Power Splitter

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

In a power-splitting PON, an optical power splitter is the passive device in the outside plant that physically connects to the CO with a feeder fiber. It also connects to a number of ONUs via a series of distribution fibers. In the past few years, significant improvements in reliability, cost per port, insertion loss, and splitting-ratio nonuniformity, have been demonstrated with planar lightwave circuit (PLC)-based splitters. Central to the splitter is a PLC chip comprising of optical waveguides fabricated on a planar substrate, typically made of silicon or quartz, to form a cascade of Y-branches. For a 1 × splitter, one side of the PLC chip is aligned to a fiber whereas the opposite side is aligned to an array of PON is typically N = 16 and N = 325, but with an increasing demand of up to N = 64， thereby making the alignment of the fiber array to the PLC chip more challenging. Compared to fused biconical-taper-based splitters, PLC technology allows for chip-size devices with the potential of integrating multiple functions, e.g. WDM coupler, onto a single clip. It also enables a more uniform loss over a wide operating range of wavelengths from 1250 nm to 1625 nm, and operaton of a wide range of temeratures from -40℃ to + 80℃. Figure 3.2 illustrates the measured insertion losses from samples of 1×32 optical splitter approved by AT&T Labs for use in the Project Lightspeed FTTH trial, showing uniform loss over a wide wavelength range.
Aside from uniform loss, the insertion loss of PLC splitters is another important parameter in network implementations that will influence system performance and the overall coast per drop. Lower insertion loss PLC slitters will extend the reach and number of customers that can be accommodated within the same PON, yielding higher revenue per PON for service providers. Aside of the theoretical splitting loss attributed to the division of optical power at the input port equally into N output ports, and given by the fromula:
Theoretical splitting loss (dB) = 10 × log10(1/N)
A PLC splitter suffers from excess insertion loss from fiber array alignment to the PLC chip, fiber array uniformity caused by pitch and depth inaccuracies in the v-grooves of fiber array block that holds the fiber array, splitting ratio uniformity caused by imperfections in the PLC chip due to manufacturing, inherent chip material loss, and inherent chip material loss, and connector loss. The targeted areas for improvement of insertion loss in PLC splitters have been in reducing connector losses, and improving fiber array and splitting ration-nonuniformity. The connector loss can be improved from 0.5 dB trough using high quality ferrules and an excellent polishing method. With advances in manufacturing process of the fiber array block and PLC chip, insertion losses from fiber array nonuniformity and splitting-ratio nouniformity can be reduced from 0.7 dB to 0.4 dB and 1.8 dB to 1.0 dB, respectively. Collectively, the excess insertion losses of PLC splitters are currently 1 – 1.5 dB above the ideal theoretical splitting loss with a nonuniformity within 2 dB over the specified range of operating wavelengths from 1250 nm to 1625 nm.
Fiber optical splitter is used to split the fiber optic light into several parts at a certain ratio . The fiber optic splitter is an important passive component used in PON FTTX networks. There are mainly two kinds of passive FTTH optical splitters: one is the traditional fused type splitter as known as FBT coupler or FBT WDM optical splitter, which features competitive price; the other is the PLC splitter based on the PLC (Planar Lightwave Circuit) technology, which has a compact size and suits for density applications. The common PLC Splitters configurations are 1×4, 1×8, 1×16, 1×32, 1×64 and 1×128, but 2×4, 2×8, 2×16, 2×32 configurations are also available.  Fiberstore singlemode& multimode FBT optical splitter comes in a wide range of split ratios with single/double/three windows. The main packages include box type and stainless tube type. The former is usually used with 2mm or 3mm outer diameter cable, while the latter is usually used with 0.9mm outer diameter cable. Our optical splitter can be terminated with your choice of connectors or installed in rack mount modules. Please contact us for the special customized needs.

The Applications and Basic Settings of OTDR

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

OTDR refers to Optical Time-Domain Reflectometer, a test instrument that analyzes the light loss in an optical fiber and verify inline splices on concatenated fiber optic cables and locate faults. If you use fiber optic cables for network connectivity, you ought to know about the applications and basic setting of OTDR.
Applications:
application of OTDR in life
OTDR can be used for return loss measurements, although quoted accuracy is not particularly high. It is very useful for measuring points loss on installed systems where it is used to find faults and measure point losses such as caused by splicing. However, to do this accurately is more complicated and time consuming than is commonly supposed. Since a measurement should be taken from both ends of the system and then averaged.
OTDR is useful for testing fiber optic cables. It can verify splice loss, measure length and find faults. It simply shows you where the cables are terminated and confirm the quality of the fibers, connections and splices. What’s more, OTDR trace could be also used for troubleshooting, since it can show where breaks are in fiber when trace is compared to installation documentation.
OTDR is also widely used for optical cable maintenance and construction. Because it can evaluate the fiber cable length, measure optical transmission and connection attenuation, as well as detect the faulty location of the fiber links.
In addition to fiber characterization, OTDR can also be used for sensing chemicals and gases. Because certain substances cause changes to the light guiding properties of the fiber and those can be observed as changes in the measurement curve.
According to the contents above, we could learn that OTDR is a valuable fiber optic tester in many applications. However, if you use it in an improper way, it can be misleading and can lead to some unnecessary mistakes. So it is necessary to understand some basic settings when using OTDR. Using an OTDR is not very difficult, but it does require familiarity. Here are some tips on how to minimize the chance of making a costly mistake.
Basic Settings:
Fiber Type – first you should choose singlemode or multimode.
Wavelength – you usually start with 850 nm on multimode fiber and 1310 nm on singlemode, since the shorter wavelength has more backscatter so the trace will be less noisy.
Measurement Parameters – the typical parameters to be set are distance range, resolution, and pulse width.
Event Threshold – it determines how much loss or change will be tagged as an event.
Index of Refraction – it is the speed of light in the fiber. You can obtain this figure from the fiber manufacturer. In most cases, you can take it directly from a standard specific sheet.
Display Units – they are usually labeled in feet or meters.
Storage Memory – this should be cleared so a new figure can be saved or stored.
Dead Zone Jumper – you must connect this fiber which should be sufficiently long between the OTDR and the fiber under test. Sometimes you may also have to connect it at the far end of the cable.

 

Things You Should Know Before Choosing an OTDR

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

OTDR that is short for optical time domain reflectometry, is a fiber optic tester for the characterization of optical networks that support telecommunications. It can be used to measure loss, optical return loss (ORL) and optical distance on a fiber optic link. Besides, by providing pictorial trace signatures of the fibers under test, an OTDR can offer a graphical representation of the entire fiber optic link. However, there are so many OTDR brands in the market. Choosing the right OTDR for your application can be challenging. So this post is intended for giving some reminders when choosing an OTDR. Hope it may help you.
Why You Need an OTDR?
As we all know, fiber testing is an essential procedure to make sure that the network is optimized to deliver reliable and robust services without fault. So here are two reasons for why an OTDR is needed.
First, service providers and network operators want to insure that their investments into fiber networks are protected. Installers need to use OTDR performing bi-directional tests and providing accurate cable documentation to certify their work. Of course, OTDRs can be used for troubleshooting problems such as break locations due to dig-ups.
Second, premises fiber networks have tight loss budgets and less room for error. Therefore installers have to test the overall loss budget with a light source and power meter, which is a big task. While OTDR can easily pinpoint the causes for excess loss and verify that splices and connections are within appropriate tolerances, which saves lots of time. Besides, it is also the only way to know the exact location of a fault or a break.
What and Where Will You Test?
Before choosing a suitable OTDR, ask yourself the following two questions.
Loss, reflectance, splicing alignment and distance, which one are you going to test? Make sure the OTDR you choose can do what you want easily, quickly and accurately. If you need to make “live” test (like during a “hot cut”—splicing of fibers in a working cable), you need an OTDR that can do an active splice loss measurement in “real time”.
Where are you going to do testing? A good understanding of the applications of an OTDR will help you make the right choice for specific needs. For example, what kind of networks will you test? LAN (local area network), metro or long haul? What is the maximum distance you might have to test? 700 m, 25 km, 150 km?
What Should Be Focused on When Choosing an OTDR?
Many people may be familiar with OTDR but not know how to choose a real right one. Except for the quality that we must focus on, the following three factors also should be attached great importance to.
A Simplified and Task-focused User Interface
Maintaining fiber health is just as challenging and makes fast troubleshooting critical. Almost every OTDR on the market today is designed to cover carrier applications. As a result, many OTDR have very complex user interfaces which require the user to make sense numerous buttons and controls and navigate cumbersome multi-level menus. It’s bad for users improving operating efficiency. So a simplified and task-focused user interface test equipment is important.
Precision Fiber Channel Information
With the wide use of short patch fibers and various types of fiber connectors, details on network link—loss, connector and reflectance—are critical to ensuring performance. However, OTDR with an attenuation dead zone of more than 3m are no longer applicable for testing data center fiber. But when problems arise, an OTDR with precision fiber channel information can help users with various skill levels efficiently perform troubleshooting and accelerate network recovery.
Effective Planning and Documentation
As data centers grow and change, it’s challenging to ensure all fibers are installed with certificated quality. Therefore, integrated project management capabilities with cable-by-cable granularity can save time and planning effort. An OTDR with built-in project management capability that allows users plan day-to-day activities without using a personal computer or laptop.

 

QSFP28 100G Transceivers & DAC Guide

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.

Four Basic Elements in a WDM System

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

We know that fiber can carry more data over long distances than any other physical medium. That makes fiber a very precious material. And how to make the most use of your fiber plant becomes a question. So there comes Wavelength Division Multiplexing (WDM).
Why Should We Deploy WDM ?
WDM can multiply your fiber capacity by creating virtual fibers. The foundation of WDM lies in the ability to send different data types over fiber networks in the form of light. By allowing different light channels, each with a unique wavelength, to be sent simultaneously over an optical fiber network, a single virtual fiber network is created. Instead of using multiple fibers for each and every service, a single fiber can be shared for several services. In this way WDM increases the bandwidth and maximizes the usefulness of fiber. Since fiber rental or purchase accounts for a large share of networking costs, substantial costs can be saved through the application of WDM. Next I will introduce to you the basic four elements in the form of a WDM system.
The Core Technology of WDM System
Generally speaking, a WDM system consists of four elements, that are transceiver, multiplexer, patch cord and dark fiber. The following text will explain them to you respectively.
Fiber Optic Transceivers. Optical transceivers are wavelength-specific lasers that convert data signals from SAN or WAN to optical signals that can be transmitted into the fiber. Each data stream is converted into a signal with a light wavelength that is an unique color. Due to the physical properties of light, channels cannot interfere with each other. Therefore, all WDM wavelengths are independent. Creating virtual fiber channels in this way can reduce the number of fibers required. It also allows new channels to be connected as needed, without disrupting the existing traffic services.
Optical Multiplexers. The WDM multiplexer, sometimes referred to as the Mux, is the key to optimizing, or maximizing, the use of the fiber. The multiplexer is at the heart of the operation, gathering all the data streams together to be transported simultaneously over a single fiber. At the other end of the fiber the streams are demultiplexed and separated into different channels again.
Patch cord. The transceiver transmits the high-speed data protocols on narrow band wavelengths while the multiplexer is at the heart of the operation. The patch cable is the glue that joins these two key elements together. LC fiber patch cables are popular, which connect the output of the transceiver to the input on the multiplexer.
Dark fiber. A requisite for any WDM solution is access to a dark fiber network. The most common way of transporting optical traffic over an architecture is by using a fiber pair. One of the fibers is used for transmitting the data and the other is used for receiving the data. This allows the maximum amount of traffic to be transported. At times only a single fiber is available. Because different light colors travel on different wavelengths, a WDM system can be built regardless. One wavelength is used to send data and a second one to receive it.