Category Archives: Fiber Testers & Tools

Understanding Fiber Optic Based Light Source

Each piece of active electronics will have a variety of light sources used to transmit over the various types of fiber. The distance and bandwidth will vary with light source and quality of fiber. In most networks, fiber is used for uplink/backbone operations and connecting various buildings together on a campus. The speed and distance are a function of the core, modal bandwidth, grade of fiber and the light source, all discussed previously. Light sources of the fiber light source are offered in a variety of types. Basically there are two types of semiconductor light sources available for fiber optic communication – The LED sources and the laser sources.

Using single mode fiber for short distances can cause the receiver to be overwhelmed and an inline attenuator may be needed to introduce attenuation into the channel. With Gigabit to the desktop becoming commonplace, 10Gb/s backbones have also become more common. The SR interfaces are also becoming common in data center applications and even some desktop applications. As you can see, the higher quality fiber (or laser optimized fiber) provides for greater flexibility for a fiber plant installation. Although some variations ( 10GBase-LRM SFP+and 10GBASE-LX4) support older grades of fiber to distances 220m or greater, the equipment is more costly. In many cases, it is less expensive to upgrade fiber than to purchase the more costly components that also carry increased maintenance costs over time.

Light sources of the fiber light source are offered in a variety of types. Basically there are two types of semiconductor light sources available for fiber optic communication – The LED sources and the laser sources.

In fiber-optics-based solution design, a bright light source such as a laser sends light through an optical fiber, called laser light source . Along the length of the fiber is an ultraviolet-light-treated region called a “fiber grating.” The grating deflects the light so that it exits perpendicularly to the length of the fiber as a long, expanding rectangle of light. This optical rectangle is then collimated by a cylindrical lens, such that the rectangle illuminates objects of interest at various distances from the source. The bright rectangle allows line scan cameras to sort products at higher speeds with improved accuracy.

The laser fiber-based light source combines all the ideal features necessary for accurate and efficient scanning: uniform, intense illumination over a rectangular region; a directional beam that avoids wasting unused light by only illuminating the rectangle; and a “cool” source that does not heat up the objects to be imaged. Currently employed light sources such as tungsten halogen lamps or arrays of light-emitting diodes lack at least one of these features.

Guide To Single Mode Fiber




As you know, there are two basic types of fiber optic system: multimode fiber and single-mode fiber. Multimode fiber is best designed for short transmission distances, and is suited for use in LAN systems and video surveillance. Single-mode fiber is best designed for longer transmission distances, making it suitable for long-distance telephony and multichannel television broadcast systems. For better understanding single mode fiber, I will list related information below.
 
Single Mode Fiber: Single Mode fibers have a small glass core, typically around 9 , can only send a pattern of light. Therefore, the intermodal dispersion is small, suitable for long-distance communication, but there is still a material dispersion and waveguide dispersion, so that single-mode fiber has higher requirements in the light source spectral width and stability, refers narrower spectral width, better stability. Later it was found at 1.31 m wavelength, single-mode fiber material dispersion and waveguide dispersion one is positive, another is negative, the number are just the same. So, 1.31��m wavelength fiber optic communication has become a very ideal working window, is now the main working band in practical fiber optic communication systems. The main parameters of 1.31��m conventional single-mode fiber are determined by the International Telecommunication Union ITU-T in recommendation G652, so this fiber optic is also known as G652.
 
The description of "Single-mode fiber" in the academic literature: General v is less than 2.405, the fiber has only one peak through, so called single-mode fiber, its core is very small, about 3 -10 microns, modal dispersion is small. The main factors affecting the fiber optical transmission band width are various dispersions, but mode dispersion is the most important. Dispersion of single mode fiber is small, so it can make light with a wide band transmission over long distances.
 
Single-mode fiber has a core diameter of 10 micron, allows single beam transmission, can relief the limitation of bandwidth and Modal dispersion. Because the single-mode fiber core is too small in diameter, it is difficult to control the beam transmission, so it needs extremely expensive laser as fiber optic light source, and the main limitation of the single mode fiber optical cable is Material dispersion, single mode fiber optical cable mainly using laser to obtain high bandwidth, because LED will release a large number of light source with different bandwidth, so the material dispersion requirement is very important.
 
Compared with multimode fiber, single-mode fiber can support longer transmission distance, in the 100Mbps Ethernet and 1Gigabit network, single-mode fiber can even support more than 5000m transmission distance.
 
From a cost perspective, due to fiber optic transceiver is very expensive, so the cost of using single mode fiber is higher than that of multimode fiber optic cable.

Cisco Leads 100G Ethernet Switch Market

In first quarter of 2013, the worldwide Ethernet switch market was $ 4.7 billion, decreased by 8% compared with 2012Q4, but an increase of 1%. 40G is the only port shipment growth products, an increase of 2%, which was mainly due to 40G fixed switches (such as 16xQSFP+) and chassis-based switches 40G line cards. Cisco is the early leader in 100G Ethernet switch port.

Due to the influence of seasonal factors, in first quarter of 2013, the Ethernet switch sales fell, but the past three quarters, the overall is still increased, taking into account the continued weakness in Europe and the U.S. federal government expense decreased , this is a positive signal.

In first quarter of 2013, port shipments fell 4%. 10G, which is generally considered as a star product, the chain fell highest.

40G is the only port shipment growth products, an increase of 2%, which was mainly due to 40G fixed switches (such as 16xQSFP +) and chassis-based switches 40G line cards.

Almost all of the Ethernet switch equipment manufacturers on a quarter-on-quarter drop.

Cisco is the early leader in 100G Ethernet switch port.

The Advantages of VDSL2

VDSL2 applied the same DMT modulation technology with ADSL2+, can be backward compatible with ADSL2+, and work within the 2.2 MHz band of ADSL2 + technology, compared to VDSL2 it can work to 17 MHz even 30 MHz band, divided more muck channel up and down, in a short distance can provide higher bandwidth, so the ADSL2+ technology usually locate on board the DSLAM equipment, and VDSL2 suitable for distance shorter FTTC outdoor cabinets or FTTB corridor solution.

Another advantage for adopting the VDSL2 is the terminal. VDSL2 terminal with ADSL2+ terminal on the appearance and usage is not big different, users continue to use copper network for broadband access, compared to the fiber-to-the-home FTTH patch cables without changing family walk line and decorate, also need not worry about the security implications of laser to human eyes. And VDSL2 backward compatible function can guarantee when equipment upgrades the original ADSL2+ terminal can still continue to use, can guarantee the smooth transition. Terminal management can continue to use as same with ADSL2+ management protocols and management systems, terminal management practices and operational methods remain the same. With the heavy use of VDSL2 terminal, VDSL2 terminal there will be more price cut space, further reduce the cost of network creation.

The Biggest Ratio eOTDR Prototype

Huawei announced that they have successfully developed the industry’s largest spectral built-in optical time domain reflection tester, which maximum support is 1:64, through the network simulation, its precision is up to 5 meters. The technique breakthrough marked the eOTDR technology has reached FTTHPON network commercial networking requirements.

Embedded Optical Time Domain Reflectometer, which is short for eOTDR. It’s the utilization of scattering light in optical fiber transmission and precision instrument, is mainly used for optical fiber quality detection and fault location, etc. Traditional external OTDR test system in PON FTTH network maintenance and fault detection, the need to change the ODN physical optical fiber connection, the system has high cost, difficult to implement.

With the development of FTTx, optical fiber developed quickly. Operators increase investments for fiber optic network year by year. How to manage cables management quickly and efficiently, to reduce OPEX, become the urgent demand of operators FTTx network construction.

Huawei eOTDR prototype through the built-in OTDR in OLTPON optical module, which can judge the fiber’s physical connection. At the same time, the built-in OTDR module and ordinary optical module size is consistent. Operators will place ordinary optical module with built-in OTDR optical module, but can not change the FTTx fiber physical network, also do not need ONT extra coordinate positioning, to avoid the external engineering of OTDR test, shorten the time needed for a fiber fault location, reduce the fiber optic fault management costs.

The industry mainstream manufacturers provide 1:8 eOTDR product ratio, after many years of technical research and experimental verification, the breakthrough to develop the  1:64 eOTDR prototype, covering the mainstream of FTTH patch cables construction scene, marked the eOTDR technology realized, breakthroughs from lab scale to commercial technological.