Difference between Laser Light Source and LED Light Source

As the wide application of fiber optic system, optical light source plays a more and more important part in it. We known a basic optical fiber system consists of a transmitter, an optical fiber and a receiver. The fiber optic light source, as an important component of the transmitter is modulated by a suitable drive circuit in accordance with the signals to be transmitted. Optical light source are also needed for performing fiber optic network testing to measure the fiber optic loss in the cable plant. Light source are offered in a variety of types including LED, halogen and laser. Among which, LED and Laser light source are two types of semiconductor light sources. The following article will discuss about some differences between laser and Led light source.
Basically, both kind of light source must be able to turn on and off millions to billons of times per second while projecting a near microscopic beam of light into an optical fiber. During the working process of optical signals, they are both supposed to be switched on and off rapidly and accurately enough to properly transmit the signals.
General difference between them as that LEDS is the standard light source which is short for light-emitting diodes. Laser light source like gas lasers may be mainly used in some special cases. Lasers are more powerful and operate at faster speeds than LEDs, and they can also transmit light farther with fewer errors. Laser are also much more expensive than LEDs.
LED fiber optic light source are made of materials that influence the wavelengths of light that are emitted. A basic LED light source is a semiconductor diode with a p region and an n region. When the LED is forward biased, current flows through the LED. As current flows through the LED, the junction where the p and n regions meet emits random photons. LEDs emitting in the window of 820 to 870 nm are usually gallium aluminum arsenide (GaAIAs). Laser is also a semiconductor diode with a p and an n region like LED, but it provide stimulated emission rather than the simplex spontaneous emission of LEDs. The main difference between a LED and a laser is that the laser has an optical cavity required for lasting. The cavity is formed by cleaving the opposite end of the chip to form highly parallel, reflective, mirror like finishes.
VCSEL is a popular laser source for high speed networking, which consist of two oppositely oppositely-doped Distributed Bragg Reflectors (DBR) with a cavity layer. It combines high bandwidth with low cost and is an ideal choice for the gigabit networking options.
Different wavelengths travel through a fiber at different velocities as a result of material dispersion. What should always keep in mind is that both Laser and LED will not emit a single wavelength, but a range of wavelength that is known as the spectral width of the source. Fiber optic light source is always works with the fiber optic power meter. During the working process, it collimated beams of light and aim right down the center of the narrow single mode core and propagates in essentially a single mode transmission. By more questions about fiber optic test equipment, such as visual fault locators, optical power meter, OTDR testers, and more. please go for FiberStore webstore.

Working Principle and Characteristics of OTDR

OTDR, the full name of which is Optical Time Domain Reflectometer, is a precise optoelectronic integrated fiber optic test equipment that produced by use of the backscatter during the Rayleigh scattering and Fresnel reflecting in the optical transmission. OTDR tester are widely used for optical cable maintenance and construction, and it can be used for the evaluating the fiber cable length, measuring optical transmission and connection attenuation, detecting the fault location of the fiber links, etc.
During the process of OTDR testing, the instrument inject a higher power laser or fiber optic light source pulse into a fiber from one end of the fiber cable, at the OTDR port to receive the return information. When the optical pulse is transmitted through the fiber, due to the nature of the fiber itself, the connector, the engagement points, bending or other similar event, there will be a scattered reflection. Part of the scattering and reflection will return to the OTDR. Useful information returned will be measured by the OTDR detector, and act as the time or curve segments of fibers at different positions. By recording the time used of the signals from transmission to returning, the transmission speed of the light in the glass fibers, the distance can be calculated.
OTDR testing has some limitation when it come to the applications for measuring the outside able plant loss. The OTDR tester will not be always sufficiently for testing. The OTDR will not work well with short cables in a building or LAN environment. The source and power meter should be used for these tasks as a result of the OTDR is not equipped to show actual cable plant loss.
OTDR use Rayleigh scatting and Fresnel reflection to characterize fibers’ characteristics. Rayleigh scattering refers to the irregular scattering generated when the optical signals transmitting in the fiber. OTDR only measure the scattered light back on the OTDR port. The backscatter signal show the attenuation degree (loss/distance) of the optical fiber, and will be tracked as a downward curve, illustrating the power of backscatter is decreasing, this is because that both transmission signal and backscatter loss are attenuated.
Given the optical parameters, Rayleigh scattering power can be marked, if the wavelength is know, it is proportional with the pulse width of the signal: the longer the pulse width, the stronger backscatter power. Rayleigh scattering power is also related to the wavelength of transmitted signal: the shorter the wavelength, the power is stronger. That is to say, the backscatter loose generated by the trajectory of 1310nm will higher than that of 1550nm signals.
In the higher wavelength region (more than 1500nm), the Rayleigh scattering will continue to decrease, and the other one phenomenon which called infrared attenuation (or absorption) will appear to increase and cause an increase the overall attenuation values. Therefore, 1550nm wavelength is the lowest attenuation, this also explains why it is a long distance communication wavelength. Naturally, these phenomena will return to affect the OTDR. OTDR of 1550nm wavelength is also have low attenuation, so it can be used for long distance testing. While as the high attenuation wavelength 1310nm or 1625nm, OTDR testing distance is bound to be limited, because the test equipment need to test a sharp front in the OTDR trace, and the end of the spikes will quickly fall into the noise area.
Fresnel reflection is discrete reflection, which is caused by the individual point of the whole fibers. These points are caused by a change in reverse coefficient elements such as glass and the air gap. At these points, there will be a strong backscattering light reflected back. Therefore, OTDR is using the information of Fresnel reflection to locate the connection point, fiber optic terminal or breakpoints.
An OTDR tester is essentially an optical radar: it sends out a flash of bright light, and measures the intensity of echo or reflections. This weak signal is averaged to reduce detection noise, and computation is used to display a trace and make a number of mathematical deductions.

Fluke Networks NetTool Series II Inline Network Tester Provided by FiberStore

Fluke Networks is the recognized leader in network testing industry. Fluke Networks provides innovative solutions, the so called Fluke network tester equipments for the testing, monitoring and analysis of enterprise networks and telecommunications networks, as well as the composition of the network infrastructure installation and certification of the fiber and copper.

As we can see, troubleshooting network connectivity problems can be a daunting and time-consuming task without the right tool, we need to spend hours of unnecessary time with trial and error guesswork trying to isolate the problem. Fluke Networks has put an end to the guessing game with the NetTool Series II Inline Network Tester.

The Fluke NetTool combines powerful NetProve diagnostics, inline Gigabit vision, VoIP Phone PC configuration testing in one palm-sized tool, so you'll have everything you need to quickly resolve even the toughest connectivity problem. Plus, with the NetSecure option, you'll have the power to identify port-based security threats and maintain user connectivity in802.1xenvironments. The Fluke Networks NetTool Series II includes NTS2-PRO, NTS2-VOIP, NTS2-NSKIT.

Fluke Fluke the NetTool II Overview
NetProve diagnosis - quickly locate the device and application connectivity problems
Inline Gigabit - online insight into the 10/100/Gig link between the switches, PC, IP phone and other devices to quickly resolve network problems with
Monitoring and verification - port monitoring to identify spyware, malware and viruses; 802.1X log solve the verification problem
VoIP troubleshooting - online connection, in-depth insight into VoIP calls to quickly diagnose IP phone boot, and call control problems and to measure key call quality metrics
PoE Measurements - verify readiness of PoE systems and troubleshoot PoE device problems
Discover available network resources - View active servers, routers and printers to provide the MAC address and IP address, subnet and related services
IntelliTone digital signal generator - quickly and securely positioned in the run network cable

Highlights
Monitoring and Authentication
NetProve Diagnostics
Inline Functionality
VoIP Test and Troubleshoot
PoE Measurements
IntelliTone Digital Signaling
Reports
Ease of Use
Screen Shots

FiberStore is one of the reputable online fiber optic test equipment sellers that have many speed and accurate Fluke testing instruments. Since no two networks are identical, FiberStore’s Fluke test equipment series offers several Fluke NetTool models and options to match your individual requirements and to maximize the value of your NetTool investment. From our top-of-the-line NetTool Series II Network Service Kit to the entry-level NetTool 10/100, you will find a Net Tool model that fits your network troubleshooting needs and your budget.

Steps for Fiber Optic Cable Termination

Fiber optic cabling is a important aspect of local area networking（LAN）communications infrastructures. fiber optic cables are being used in an increasing number of applications, especially in networking and cable/ Internet. In fiber networking installations, workmanship is critical to reach acceptable results because even a small imperfection or microscopic dirt on the face of the fiber can result in significant problems with optical propagation, which can cause the link to fail. This article offers a hands-on tutorial for fast, safely, and correctly creating fiber optic connections that meet good standards of quality workmanship and ensure optimal coupling efficiency. The following steps for fiber optic cable termination with epoxy will help installer avoid problems by providing a solid base of information that will have great reference value for both new and experienced field technicians terminating fiber optic cables often.

Step1. Creating and maintaining a safe work environment.
You should not only protect yourself during the installation process, you also need to leave the installation area in a safe condition for other people beside you. Fundamental safety tools include a dark work surface, such as a black work-mat, and a proper trash receptacle for fiber scraps that is clearly marked as to its contents. Using a piece of black tape to stick your scraps on isn't an acceptable work practice other than just incorrectly flick off the cleaved fiber scraps with fingers which could be harmful to the occupants nearby. Then, use a microscope to check a fiber to make sure the other end isn’t connected to a power source since the invisible laser light is harmful to the eyes while you may not eve realize you’re looking into it until it’s tool late..

Step2. Strip the cable with a fiber cable stripper.
Once you have your bulk fiber cable, strip the cable down to the bare fiber using an appropriate fiber stripper such as the Fiber Cable Stripper. After you have prepared the end of the cable you may begin to mix the epoxy resin and hardener together and load it into a syringe, unless of course you are using pre-loaded epoxy syringes, which are premixed and kept frozen until use. Now, from the syringe you must inject the epoxy directly into the connector ferrule.

Step 3. Inject epoxy into the connector ferrule and insert the fiber optic into the connector wall.
Injet epoxy into the fiber optic connector ferrule and then insert the fiber optic cable so that the cable is seated inside of the connector wall and the bare fiber core sticks out about a half an inch from the front of the ferrule.

Step 4: Crimp the cable with the cable crimper.
If your cable is jacketed, you will need to use a crimping tool to secure the connector to the jacket and strength member of the cable. Two crimps would be needed at this point.

Step 5: Place the cable in the curing holder, suite the connector end facing down.
After that, the next step is to place the connected end into a curing holder to ensure that the end of the fiber is not damaged while curing. Now place the cable and curing holder into a curing oven. To avoid “wicking” while curing with a conventional oven, situate the connector so that the end is facing down. This positioning will ensure that the epoxy does not come out of the back side of the connector and compromise the strength member of the cable. Then you need to refer to the documentation of your specific epoxy for accurate curing times and temperatures.

Step 6: Cleave the fiber with the fiber optic cleaver. Get as close to the ferrule tip as you can.
After you have sufficiently cured the epoxy, you are now ready to move on to the next step, cleaving the excess protruding fiber core. Tool you need is a Fiber Optic Cleaver. Get as close to the ferrule tip as possible while avoiding any sort of twisting motion.

Step 7. Dispose of all fiber pieces after cleaving.
Once cleaved, it is important that you properly dispose of the fiber clipping. A regular piece of tape will do just fine at retaining your fiber debris. If you do not properly dispose of all fiber pieces they could easily end up in your skin or even in somebody’s eye or respiratory system. A short strand of fiber can cause more damage than you would at first imagine.

Step 8. Polish the end of the fiber optic cable.
After the excess fiber cleaved and properly disposed of, you can begin the task of polishing the fiber tip to a smooth finish. Using fiber optic polishing tool you can effectively remove any excess epoxy from the ferrule end and buff out any imperfections on the face of the fiber. You can polish the cable tip with the 5-15 micron film, 5 micron aluminum oxide film, 3-6 micron diamond film, 1 micron diamond film, and HX film in order. A smooth fiber surface makes great sense to any light passing through.

Step 9. Clean the ferule and fiber tip.
If you have finished with your polished finish, you can move on to the cleaning of the ferrule and fiber tip. Using a lint-free wipe dipped in 99% reagent-grade alcohol, gently wipe the surface area of the ferrule and fiber tip and immediately wipe them dry with another dry lint-free wipe. You may optionally use a can of compressed air to finish the process.

Step 10. Test the terminated cable with fiber optic test equipment.
Now the connected cable is complete. The last step is to ensure good standard. First you need to inspect the fiber tip with a 100x to 200x microscope. And then test your cable with a fiber optic test equipment for insertion loss and return loss where needed.