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The Rapid Development of FTTH Borrow PON Promote Triple Play

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The arrival of the triple play, will greatly promote the video business, such as high-definition television, as well as the future of 3D TV business rapid development of broadband services, but also broadband access network is another new challenge. FTTH can not only provide massive bandwidth support business, and low operating costs, therefore, FTTH mode will gradually become the mainstream of triple play network construction in 2010 years to achieve scale deployment.
Significant advantages of FTTH
In the past few years, carriers generally adopted EPON technology, by the large-scale depolyment of FTTB/FTTN original access network of optical fibers and speed to achieve from the original 512K “narrow” broadband to 4M/8M/12M high bandwidth upgrade but with the growing popularity of high-definition television and other the severe erosion bandwith video class of business in the next few years, due to the limited bandwidth of EPON can prodive effective, as well as the number of users more brought under a single PON port existing mode will lead to the present FTTB-based access network to turn highlights powerless in the next era of full-service, bandwidth bottlenecks. Continues to mature as the whole industry chain, the end-to-end cost of each line of FTTH has dropped to about 1,000 yuan, has reached the scale deployment costs level, especially in the new area, FTTH FTTB cost disadvantage compared to the gradual narrow, basically reached the same level. Taking into account the FTTH can provide massive bandwidth, business support, and teh operating costs are vey low, FTTH mode will gradually become the mainstream, and achieve economies of scale deployments in 2010.
High quality FTTH
Shanghai Bell as leading technology PON equipment manufacturers, has launched GPON/EPON/10GPON mixed interpolation solutions based on the original 7342 platform, together with a light terminal series to meet operators under different scenarios and business needs FTTH deployment. The Shanghai Bell and Verizon the asymmetric 10G GPON current network pilot. Shanghai Bell will strive to promote 10GPON mature early realization of its commercial deployment.
GPON for FTTH deployment
In FTTH scenario, because GPON splitting ration can be achieved 1:128, with better network planning flexibility, mobility and bandwidth scheduling, can effectively reduce the sunk cost. GPON offers higher effective downlink bandwidth and better QoS guarantee. In addition, in the process of upgrading to the next generation 10G PON compared to EPON, GPON can achieve a smoother evolution.
Completely isolated 10G GPON GPON up and down the line wavelength, wavelength division superposition can be used, in the case does not change the current network deployment OLT / ONT / ODN smooth upgrade. Upstream wavelength and 10GEPON and EPON overlap, so using time division multiplexing manner compatible with the existing network deployment EPON ONU, which will lead to all central office OLT line card with new the line of 10GEPON card to replace this deployment of existing network services and devices serious. Therefore, GPON technology is more suitable for the construction of the FTTH network.

 

How to Realize Single Fiber Connection in WDM System?

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As we all know, fiber optical networking has two transmission ways: dual fiber transmission and single fiber transmission. The difference between them is that the former one requires two fibers—one is for transmitting and the other is for receiving, while the latter only uses one fiber for both transmitting and receiving. Single fiber transmission emergence reduces network deployment cost, especially in WDM systems. This blog intends to introduce how to achieve single fiber connections in CWDM and DWDM networks.
Understanding Single Fiber Transmission
Single fiber transmission, also called bidirectional (BiDi) transmission, sends data in both directions with one strand fiber. For enterprise networks or telecom networks providers who are with limited budgets and fiber capacity, the single fiber transmission is no doubt an ideal choice.
In addition, single fiber transmission is popular in many places.
Point to Point, Ring or linear Add and Drop, where installing new fiber is difficult or expensive
Enable segmentation of the enterprise traffic over 2 different fibers rather than using the same fiber for both segments
Increase reliability to an existing dual fiber solution by using one fiber for working and one for protecting.
Single Fiber Solution in CWDM Systems
CWDM technology enables multiple channels (wavelengths) to be transmitted over the same fiber cabling and is able to provide a capacity boost in metro and access networks. Each channel carries data independently from each other, which allows network providers to transport different data rates and protocols (T1, T3, Ethernet, Serial, etc) for different customers or applications. Then how to achieve single fiber transmission in CWDM networks?
Here is an example of single fiber solution in CWDM system.
8-ch-single-fiber-cwdm-mux-demux
The above picture shows how different CWDM wavelengths are transmitted in a single fiber CWDM link. In this link, two 8CH CWDM Mux/Demuxs are required to transmit sixteen different wavelengths. At site A, there is a single fiber 8CH CWDM Mux/Demux using eight wavelengths for transmitting and the other different eight wavelengths for receiving. At site B, another 8CH single fiber CWDM Mux/Demux is deployed. But the wavelengths for TX and RX are reversed. And one single fiber connects the two CWDM Mux/Demux.
Notes: the use of transceivers connected with the CWDM Mux/Demux should be based on the wavelength of the TX side.
Single Fiber Solution in DWDM Systems
DWDM is an optical multiplexing technology to increase bandwidth over existing fiber optic networks, especially in long haul transmissions. And it can support more channels and higher traffic services such as 40G, 100G of LAN/WAN. Since the cost of DWDM components is high, the single fiber transmission is necessary.
DWDM single fiber transmission can be achieved with the use of single fiber DWDM Mux/Demux. As the following picture shows.
DWDM single fiber solution
The picture shows a single fiber 8CH DWDM Mux/Demux with expansion port used for single fiber transmission. Similar to the single fiber CWDM Mux/Demux above, this DWDM Mux/Demux also uses eight wavelengths for transmitting and another eight wavelengths for receiving. In general, the DWDM Mux/Demux should be used in pairs in single fiber bi-directional transmission, and the Mux/Demux port for specific channel must be reversed. Besides, more channels can be added into the links with the expansion port.
This 8CH DWDM Mux/Demux single fiber solution allows extremely high utilizing of a single fiber strand to pass up to 16 wavelengths, optimizing the use of fiber optic cables. And in long distance transmission, optical amplifier also can be utilized.

Understanding WDM MUX/DEMUX Ports and Its Application

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Wavelength division multiplexing (WDM) is a commonly used technology in optical communications. It combines multiple wavelengths to transmit signals on a single fiber. To realize this process, CWDM and DWDM mux/demux are the essential part. As we all know, there are several different ports on the WDM mux and demux. This article will give a clear explanation to these ports and their applications in WDM network.
Overview of Different Ports on WDM MUX/DEMUX
Line Port
Line port, sometimes also called as common port, is the one of the must-have ports on CWDM and DWDM Mux/Demux. The outside fibers are connected to the Mux/Demux unit through this port, and they are often marked as Tx and Rx. All the WDM channels are multiplexed and demultiplexed over this port.
Channel Port
Like the line port, channel ports are another must-have ports. They transmit and receive signals on specific WDM wavelengths. CWDM Mux/Demux supports up to 18 channels from 1270nm to 1610nm with a channel space of 20nm. While DWDM Mux/Demux uses wavelengths from 1470nm to 1625nm usually with channel space of 0.8nm (100GHz) or 0.4nm (50GHz). Services or circuits can be added in any order to the Mux/Demux unit.
40ch dwdm mux demux
Monitor Port
Monitor port on CWDM and DWDM Mux/Demux offers a way to test the dB level of the signal without service interruption, which enable users the ability to monitor and troubleshoot networks. If the Mux/Demux is a sing-fiber unit, the monitor port also should be a simplex one, and vice verse.
Expansion Port
Expansion port on WDM Mux/Demux is used to add or expand more wavelengths or channels to the network. By using this port, network managers can increase the network capacity easily by connecting the expansion port with the line port of another Mux/Demux supporting different wavelengths. However, not every WDM Mux/Demux has an expansion port.
dwdm mux demux
1310nm and 1550nm Port
1310nm and 1550nm are one of WDM wavelengths. Many optical transceivers, especially the CWDM and DWDM SFP/SFP+ transceiver, support long runs transmission over these two wavelengths. By connecting with the same wavelength optical transceivers, these two ports can be used to add 1310nm or 1550nm wavelengths into existing WDM networks.
Application Cases of Different Ports on WDM MUX/DEMUX
Although there are several different ports on WDM Mux/Demux, not all of them are used at the same time. Here are some examples of these functioning ports in different connections.
Example One: Using 8 Channels CWDM Mux/Demux with Monitor Port
cwdm mux demux with monitor port
This example is a typical point-to-point network where two switches/routers are connected over CWDM wavelength 1511nm. The CWDM Mux/Demux used has a monitor port and 1310nm port, but the 1310nm does not put into use. In addition, an optical power meter is used to monitor the power on fibers connecting the site A and B.
Example Two: Achieve 500Gbps at Existing Fiber Network with 1310nm Port
dwdm mux with 1310nm port
In this example, two 40 channels DWDM Mux/Demux with monitor port and 1310nm port are used to achieve total 500Gbps services. How to achieve this? First, plug a 1310nm 40G or 100G fiber optical transceiver into the terminal equipment, then use the patch cable to connect it to the existing DWDM network via the 1310nm port on the DWDM Mux/Demux. Since the 1310nm port is combined into a 40 channels DWDM Mux, then this set-up allows the transport of up to 40x10Gbps plus 100Gbpx over one fiber pair, which is total 500Gbps. If use 1550nm port, then the transceiver should be available on the wavelength of 1550nm.
cwdm mux with expansion port
The connection in this example is similar to the last one. The difference is that this connection is achieved with expansion port not 1310nm port. On the left side in the cases, a 8 channels CWDM Mux/Demux and a 4 channels CWDM Mux/Demux are stacked via the expansion port on the latter Mux/Demux. And the two 4 channels CWDM Mux/Demux are combined with the line port. If there is a need, more Mux/Demux modules can be added to increase the wavelengths and expand network capacity.

The Difference Between Loose Tube Fiber and Tight Buffer Fiber

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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

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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

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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.