Fiber Optic Cabling Facts: 10 Things You Might Not Know – Part 1

by Fiber-MART.COM

All over the world, people are really beginning to embrace the power and the flexibility of fiber optic cabling. While the technology behind the new fiber optic cabling installations is not exactly brand new, the applications in which it’s being called to use for are and it’s exciting to see. Due to a wide variety of reasons, fiber optic cabling is becoming the fastest, smartest and most flexible way to enable large amounts of digital data to be transmitted and received. The only problem is, many people are still in the dark about fiber optic cabling technology.

 

To attempt to slightly remedy that situation, we’re going to present the first 5 of 10 interesting and exciting about fiber optic cabling today that should shine some “light” on such a great technology. Here are our favorite fiber optic cabling facts:

 

Fiber Optics Has a History – The technology surrounding fiber optics has been around since the 1870’s. The first introduction of actual fiber optic cabling started showing up in the 1950’s. This is a technology rooted in solid history.

 

Fiber Optics Use Light – There is no electrical current being passed through fiber optic cabling, only light. Because of this, there is no heat and no heat means no burning and no fire hazards. During normal use, fiber optics are the safest option for data transmission.

 

Fiber Optics are FAST – Data can be transmitted through fiber optic cabling faster than traditional cabling due to increased capacity. Right now, commercial uses of fiber optic cabling can transmit 10-80 Gigabits per second over just one channel. According to reports, the current record is 15.5 Terabits per second over a distance of 7,000km. To put that into perspective, that’s the equivalent of 10.3 million DSL connections.

 

Fiber Optics Have Many Uses – From the traditional use of data transmission, fiber optics have grown in their use. Now, they are used with gun sights, imaging optics, spectroscopy, supply low levels of power, signs, art and even artificial Christmas trees.

Fiber Optics are Green – The amount of energy required to send a flash of light across a distance in fiber optic cables is far less than that required to send electrical signals. Less power means less carbon output, lower emissions and lower prices.

There is the first half of our 10 favorite facts about fiber optic cabling. As you can already tell, fiber optics are an interesting and exciting development in data transmission technology. Stay tuned for our next installment and the remaining 5 fiber optic cabling facts!

 

To learn more about fiber optic cabling installations and how the technology can help push your company into the next level, please feel free to visit fiber-mart’s Fiber Optic Cabling page.

Are polymer waveguides in the future for the fiber optic industry?

Since the early 1970s, the demand for higher communication and information traffic has caused the optical fiber network to burgeon. In fact, the modern fiber optic network comprises a large part of the Internet backbone. This includes long-distance communication cables containing optical fibers that are routed under the sea and through underground conduits – optical fibers that interconnect data centers around the world and bring fiber to the office (FTTO) and fiber to the home (FTTH).

 

In recent years, the growth of the fiber optic industry has been even more explosive. Fiber optic technology has expanded into short-distance connections between devices such as computer networking, high-definition televisions, and motherboards and devices within computers. Optical glass fiber, which is highly engineered in structure for multimode and singlemode, has evolved – as have most plastic optical fibers used for very-short-distance communications. Many companies have contributed to the proliferation of fiber’s uses and forms including (to name a few) Alcatel, AT&T, Ciena, Cisco, Corning, Finisar, JDS Uniphase, Lucent Technologies, and Tyco.

 

Making fiber optic cables for the huge diversity of the fiber network is a multibillion-dollar industry. Fiber optic cables – both outdoor and indoor patch cords and interlinks – need to assume a wide variety of custom form factors to accomplish all the different kinds of interconnection that is needed. A typical fiber optic patch cord is a glass optical fiber that is terminated at either end with connectors (such as SC, LC, and MTs), which allow the patch cord to be rapidly and reliably connected to other functional devices such as optical switches, optical couplers, amplifiers, and WDMs. The technology of fiber optic termination involves specialized epoxies, mirror polishing, inspection, and testing for continuity and performance.

 

The development of polymer waveguides as an alternate solution

In the early 1980s, engineers at DuPont foresaw the need for a more easily produced, customized fiber optic assembly. In 1985, they demonstrated a waveguide that was photo-imaged in a polymer film. Between 1985 and 1998, DuPont developed a technology – and later spun out the company Optical InterLinks (OIL) – to make high-performance, low-cost, manufacturable optical data devices.

 

The technology uses a polymer waveguide: a flexible, self-supporting, polymer film developed using a photo-image process, which allows rapid duplication. Producible features include splitters/combiners, graded or step index profiles, and optical shuffles. Easily incorporated are 90-degree interconnections with I/O mirrors, mirror/surface reflectors, and other optical surfaces. This technology enables highly compact customized optical probes and sensors. By using matrix processes, optical sensors can also be produced using this type of process where two intersecting fibers transfer optical power as pressure distorts their waveguide paths, thus creating a “cross-talk” function. Low-cost sensors in matrix format could be mass produced that easily measure pressure points, analogous to how a hand holds a glass with palm and finger pads.

 

This automated process could enable high-volume applications for short-distance communications such as the automotive data bus. As cars become more and more complex, the use of highly reproducible plastic optical fiber bus systems that are inexpensive to reproduce in quantities of thousands (or hundreds of thousands) are critical. In researching this topic, part of my process included contacting Wayne Kachmar through his company, Technical Horsepower Consulting, for consultation on the Optical InterLinks (OIL) polymer waveguides technology. Mr. Kachmar’s experience – over 38 years of optical fiber cable design, testing, specification creation and installation – gave me additional insight into overarching industry trends and specific opportunities regarding this technology. According to optical cable expert Wayne Kachmar, polymer waveguides could be a competing technology in the automotive industry for the reasons mentioned above.

 

Keep in mind that polymer waveguides are not a new technology. Between 1993 and 1997, the Defense Advanced Research Projects Agency (DARPA) supported a project in which Optical InterLinks provided the flexible polymer waveguide array between PD/VCSELs and its Parallel Optical Link Organization. Another project followed with DARPA, which is a US Department of Defense agency. Numerous publications, delivered prototypes, and publicity from DARPA projects generated market awareness and interest in polymer waveguides. In 30 years of working with this technology, Optical InterLinks has come to understand many of the subtleties of the photo-chemistry of this system to further refine the performance of the optical devices created.

 

Why hasn’t this technology caught on in the fiber optic industry?

Polymer waveguides have succeeded in generating interest, and some companies have watched this developing technology for quite some time. Every technology introduced into a market must find a niche and solve a problem. In which areas could this technology solve problems? Wayne Kachmar’s consultation with me included some of the most viable applications and opportunities, listed here:

 

Computer motherboard applications for high-speed computing

The ability to provide optical input to flexible OLED (organic LED) devices – In “wearable signage,” a screen on your shirt would receive and transmit data

Automotive networking systems – The average communications load in automobiles is closely following Moore’s Law (the amount of computing power doubles every 2 years)

 

What is preventing a major adoption of polymer waveguides in the fiber optic industry?

 

In my consultations with Optical InterLinks’ engineers and industry experts such as Wayne Kachmar, I believe there are 4 key reasons why the polymer waveguides technology has not been fully integrated into our industry:

 

Despite the fact that Optical InterLinks’ polymer waveguides technology is 30 years old, it is still very unique. In some ways, this technology is a solution that is ahead of its time. Although sensor technology, automotive data buses, and optical backplanes for computers are rapidly coming to fruition, they do not yet require the speed and simplicity that this technology represents. (Metallic conductive systems such as copper bus systems have significantly surpassed experts’ expectations, although we may be approaching the limits of copper.) Creating a photo-imaging template requires a library of photonic elements and rules for spacing, minimum radii of curvature, modal filling, and so forth. Optical InterLinks has developed many of these components for its polymer waveguides technology, but they have not yet found a solid foothold in the fiber optic industry.

 

Alternate technologies using Si and Si-based materials seek to make waveguide structures that are smaller, denser, and cheaper. Methods to integrate light sources and amplification to silicon-based solutions are being addressed by a mix of companies including system houses and (photonic) integrated circuit manufacturers, with quite a variety of competing solutions. Companies involved in the push to make light penetrate further into integrated circuits prefer to develop and maintain innovative technologies themselves. The tendency is to keep this proprietary information in-house rather than collaborate with an outside partner. Due to the lack of intellectual property connected to the polymer waveguides technology, it’s effectively an open-source technology. This means, in all likelihood, no one organization would invest a large amount of money to further develop it. On the other hand, this means the door is open for anyone to embrace the technology and integrate it into their application.

 

The advent of bend-insensitive fibers has severely limited the interest in Optical InterLinks’ polymer waveguides technology for any high-bandwidth applications. Also, the difficulty of connectorization of conventional fibers may become obsolete with the rapid advancement and acceptance of additive technology (aka 3D printing) to create (print) fiber optic connectors. These new, competing technologies – bend-insensitive fiber and additive technology – are likely to be more popular choices for applications such as optical backplanes for computers. These technologies are highly patentable, and there is potential to mass produce products using these technologies. In my discussion with Wayne Kachmar, he put forth an interesting idea: “In the automotive world, two technologies working together – additive technology and OIL’s polymer waveguides technology – could potentially be a killer solution for automotive data backbones. This niche potentially offers the volume, demand, and requirements to move polymer waveguides forward. This application could be a great match for the polymer waveguides technology.”

 

Termination of polymer waveguides is still a manual process, and needs to become more automated. However, as waveguides penetrate further into electronic chips, standard connector termination with SC, LC, and MTs will continue outside the chip almost as a pigtail. But in attaching the pigtail to the chip emitters or detectors, other methods of coupling light such as additive technology may become more common on chip. This may allow for other methods including polymer waveguide devices to enter into the inter-chip area. However, it is unlikely to change the chip-to-glass fiber interface side of the connection due to many technical details such as index of refraction mismatch, flat-to-round waveguide shapes as well as a number of other physical challenges, beginning with the difference in thermal shrinkage of polymer and glass (and therefore the silicon substrate material).

 

are-polymer-waveguides-in-the-futureConclusion

Optical InterLinks’ polymer waveguides technology has not yet found a niche in the fiber optic industry. While many innovations throughout history have multiple advocates and follow roughly parallel paths – for example, the “electrical” feud of Nikola Tesla and Thomas Edison or the “format war” of Betamax and VHS tape – usually one emerges as the preferred choice and brings standardization to the industry. For some technologies and industries where computing power is just starting to exert its influence, such as sensors and automotive systems, polymer waveguides may gain a foothold. Wayne Kachmar summed it up nicely in our discussion, “There are opportunities for this particular technology. Polymer waveguides does have promise for the fiber optic industry.”

Fiber Optic Cable are usually used in two scenarios

Fiber Optic Cable are used in applications where the optical signal is too strong and needs to be reduced. For example, in a multi-wavelength fiber optic system, you need to equalize the optical channel strength so that all the channels have similar power levels. This means to reduce stronger channels’ powers to match lower power channels.

The attenuation level is fixed at 5 dB, which means it reduces the optical power by 5dB. This attenuator has a short piece of fiber with metal ion doping that provides the specified attenuation.

There are many different mechanisms to reduce the optical power, this picture shows another mechanism used in one type of variable attenuator. Here variable means the attenuation level can be adjusted, for example, it could be from 1 dB up to 20dB.

Fiber Optic Cable are usually used in two scenarios.

The first case is in fiber optic power level testing. Cable are used to temporarily add a calibrated amount of signal loss in order to test the power level margins in a fiber optic communication system.

In the second case, Cable are permanently installed in a fiber optic communication link to properly match transmitter and receiver optical signal levels.

Simplex OM1 62.5/125 Multimode Fiber Optic Patch Cable

Optical Cable are typically classified as fixed or variable Cable.

Fixed Cable have a fixed optical power reduction number, such as 1dB, 5dB, 10dB, etc.

Variable Cable’ attenuation level can be adjusted, such as from 0.5 dB to 20dB, or even 50dB. Some variable Cable have very fine resolution, such as 0.1dB, or even 0.01dB.

This slide shows many different optical attenuator designs.

The female to female fixed Cable work like a regular adapter. But instead of minimizing insertion loss, it purposely adds some attenuation.

The female to female variable Cable are adjustable by turning a nut in the middle. The nut adjusts the air gap in the middle to achieve different attenuation levels.

The male to female fixed Cable work as fiber connectors, you can just plug in your existing fiber connector to its female side.

The in-line patch cable type variable Cable work as regular patch cables, but your can adjust its attenuation level by turning the screw.

For precise testing purposes, engineers have also designed instrument type variable Cable. These instrument type Cable have high attenuation ranges, such as from 0.5 dB to 70dB. They also have very fine resolution, such as 0.01dB. This is critical for accurate testing.

How to Measure Fiber Optic Network by Using OTDR Testers?

How to Measure Fiber Optic Network by Using OTDR Testers?

Optical fiber measurement can be divided into three steps: using OTDR testers for parameter setting, data acquisition and analysis. Measuring parameters include artificial Settings.

(1) the wavelength selection (λ):

Because of different wavelengths corresponding to different features (including attenuation, slightly curved, etc.), generally following the test wavelength and wavelength corresponds to the principle of transmission communication system, the system open 1550 wavelengths, the test wavelength of 1550nm.

 

(2) Pulse Width:

The longer the pulse width, the bigger the dynamic measurement range, measurement of distance is longer, but blind area is bigger in OTDR curve waveform; Short pulse injection of low light level, but can reduce the blind area. Usually stand by ns for pulse width cycle.

 

(3) Range:

OTDR testers measurement range is refers to the maximum distance of OTDR data sampling, the choice of this parameter determines the size of the sampling resolution. Best measurement range for 1.5 ~ 2 times the distance between optic fiber network length.

 

(4) Average time:

The backward scattering light signal is very weak, generally USES the statistical average method to improve the signal-to-noise ratio, average, the longer the average time, the higher signal-to-noise ratio.

 

(5) Parameters of optical fiber

Optical fiber parameter setting including the refractive index n and Backscatter coefficient of η. Refractive index parameters related to distance measuring, backscatter coefficient effects the measurement results of reflection and return loss.

After Parameter Settings, OTDR can be sent and received by the optical fiber link light pulse scattering and reflected light, the photodetector outputs sample, get the OTDR curve, the curve is analyzed to understand quality of optical fiber.

 

Experience and skills

(1) Simple discriminant of fiber quality

Under normal circumstances, OTDR test the light curve of the subject (single or several plate cable) slope are consistent, if a certain section of the slope is bigger, indicates the period of decay; If subject to irregular shape curve, the slope is volatile, it is bent or arc, suggests that bulk fiber cables quality degradation seriously, do not conform to the requirements of the communication.

 

(2) The choice of wavelength and the test of Uni and Bi-direction:

1550 wavelengths to test distance is farther, a 1550nm – 1550nm fiber is more sensitive to bending than 1310. In an actual optical cable maintenance, compare both wavelengths to get good test results.

(3) Clean the joint:

Before accessing optical union, must be cleaned carefully, including OTDR output fiber assembly connectors and measured union, or the insertion loss will too big, otherwise don’t reliable, much noise can stop the measurement, it may also damage the OTDR. Avoid using alcohol cleaning or other refractive index matching liquid, because they can dissolve the adhesive within optical fiber connector.

 

(4) The use of additional optical fiber

Additional optical fiber is used to connect OTDR and optical fiber which under test, 300 ~ 2000 m long fiber, its main role is: the front insert measuring blind area processing and terminal connector.

 

In general, OTDR and optical fiber connectors between blind area under test is the largest. In actual measurement of the optical fiber in the OTDR with fiber and after a period of transition, the front end blind area falls within the transition of optical fiber, the fiber under test head fell on the OTDR curve in the linear region. Optical fiber system between connector insertion loss by OTDR testers and optical fiber to measure for a period of transition. As to measure the first and end connector on both ends of the insertion loss, can add a transitional fiber in every side.

What Is The Basic Principle Of OTDR Test

There are many fiber tools available for testing at different stages of the network, to meet various test requirements. These tests are used to reveal the total loss, optical return loss (ORL) and fiber length, can be in a single fiber or a complete network. In addition, the test may require further examination of the different elements of the measured link. Whether identify the characteristics of each component in the link, locate potential problems for a fiber, or find fault in the network, all will inevitably have to use optical time domain reflectometer (OTDR) – from commissioning to the optical network troubleshooting and maintenance, OTDR is the ideal choice. This article will describe the basic principles of an otdr test, for you better understanding the instrument specifications.

What Is An OTDR?

OTDR shows the link condition by reading the light level sent back from the optical pulse. Note that there are two types of reflected light: a continuous low-level light produced by fiber is called Rayleigh backcattering light, high reflection peak at the connection point is called the Fresnel reflection. Rayleigh backscattering is used as a distance function to calculate the attenuation level in fiber optic (unit of dB/km), shown as the linear slope of OTDR trajectory. This phenomenon comes from reflection and absorption of the fiber impurities inside the inherent. When light hits on some impurities, impurity particles will redirect light in different directions, while generating a signal attenuation and backscattering. The longer wavelength, the less the attenuation. Therefore, transmit the same distance in the standard fiber requires smaller power. The below picture illustrates the Rayleigh backscattering.

 

The second reflection (Fresnel reflection) OTDR uses can detect the physical events along the link. When the light reaches the refractive index mutated position (such as from glass to air), a large part of the light is reflected back, resulting Fresnel reflection, it may be thousands of times stronger than the Rayleigh backscattering. Fresnel reflection can be identified through the OTDR track peak. Examples of such reflection are fast connectors, mechanical splices, optical fiber, fiber breaks or open connectors.

 

What Is The Blind Zone?

Fresnel reflection leads to an important specification of OTDR, namely blind spot. There are two types of blind spots: events and attenuation. Both are generated by the Fresnel reflection, with the changing distance (meters) depends on the different changes in the reflected power to represent. Blind spot is defined as the duration time, in the meantime detector by high intensity reflected light effects of temporary “blindness”, until it returns to normal can re-read the light signal, imagine, when you night driving with the oncoming cars encounter, your eyes will be short-term blindness. In the OTDR field, time is converted to distance, therefore, the more reflective the detector longer recovery time, leading to longer blind. Most manufacturers are available in the shortest possible pulse width, and single mode fiber -45 dB, -35 dB multimode fiber reflection to specify blind. Therefore, reading the table footnote of specifications is very important because manufacturers use different test conditions for measuring blind area, with particular attention to the pulse width and reflectance values. For example, single-mode fiber -55 dB reflection provides shorter blind specifications than that of -45 dB, just because -55 dB is a lower reflection, the detector recovery faster. In addition, the use of different methods to calculate the distance will be a shorter blind zone than that of the actual value.

 

Event Blind Zone

Event blind zone is the minimum distance of another event OTDR can detect after Fresnel reflection. In other words, is the minimum fiber length needed between the two reflection events. Still the diving mentioned before as an example, for example, when your eyes can not open because the glare stimulation from the opposite car, after a few seconds, you will find that there is an object on the road, but you can not identify it correctly. Turned to OTDR, can be detected by continuous event, but can not measure the loss. OTDR merging successive events, and returns to a global reflection and loss on all the combined events. To establish specifications, the most common industrial way is to measure the distance between each side of the -1.5 dB of peaks.You can also use another method, measure the distance from the event starts until the reflection level from the peak down to -1.5 dB. This method returns to a longer blind, manufacturers use less.

 

OTDR event blind zone as short as possible is very important, so that it can detect the closely spaced events in the link. For example, testing requirements of OTDR event blind zone is very short in the building network, because the fiber jumper connecting various data centers is very short. If the blind area is too long, some connectors may be missed, the technicians can’t identify them, which makes the job of positioning potential problems become more difficult.

Attenuation Blind Zone

Attenuation blind zone is after the Fresnel reflection, OTDR can accurately measure the minimum distance of successive events loss. Also use the example above, after a longer period of time, your eyes are fully restored, the ability to identify and analyze possible attributes of objects on the way. Shown below, the detector has enough time to recover, so that it can detect and measure the loss of successive events. The minimum distance required from the beginning of reflection events, until the reflection is reduced to the fiber backscattering level of 0.5 dB.

 

The Importance Of Blind Zone

The short attenuation zone makes the OTDR can not only detect the continuous events, but also can return to the close event loss. For example, you can now learn the loss of short fiber jumpers in network, which can help technicans to understand the situation within the link.

 

Blind zone also affected by other factors: pulse width. Specifications using the shortest pulse width in order to provide the shortest blind zone. However, the blind zone is not always the same length, as the pulse wider, blind spots will be stretched. Use the longest possible pulse broadband will lead to blind particularly long, but it has a different purpose.

 

Conclusion

On the market, there are many types of OTDR – from based fault locator to advanced equipment, can meet the different test and measurement requirements. To buy the right OTDR, you must consider the basic parameters. Because if the selected model is not suitable for the application, only based on the overall performance and price to choose equipment will appear problems. OTDR with complex specifications, the vast majority are a result of compromise. A deep understanding of these parameters and know how to verify these parameters can help buyers to make the right choice meeting their demand, maximizing productivity and cost effectiveness.

7 Factors to Consider before Selecting An OTDR

7 Factors to Consider before Selecting An OTDR

by Fiber-MART.COM

An OTDR (Optical Time Domain Reflectometer) is a fiber optic tester for the characterization of optical networks that support telecommunications. The purpose of an OTDR is to detect, locate, and measure elements at any location on a fiber optic link. An OTDR needs access to only one end of the link and acts like a one -dimensional radar system. By providing pictorial trace signature of the fibers under test, it’s possible to get a graphical representation of the entire fiber optic link.

FIBER-MART.COM 2405 OTDR

 

An OTDR can be used to measure optical distance including locations of the elements like splices, connectors, splitters, multiplexers and faults, as well as end of fiber. Loss and Optical Return Loss (ORL)/Reflectance, such as loss of splices and connectors, ORL of link or section, reflectance of connectors and total fiber attenuation can also be tested by OTDRs.

 

Not all OTDR are made the same. There are various kinds of OTDR models available, addressing different test and measurement needs. The choosing of an OTDR is based on applications. By thinking of the following questions, you can roughly know what kind of OTDR you need.

 

What kind of networks will you be testing? LAN, metro, long haul?

What fiber type will you be testing? Multimode or single-mode?

What is the maximum distance you might have to test? 700 m, 25 km, 150 km?

What kind of measurements will you perform? Construction(acceptance testing), troubleshooting, in-service?

JDSU MTS-4000 OTDR

 

FIBER-MART.COM offers you 7 factors to help you figure out which OTDR best fits your applications.

 

Size and Weight: important if you have to climb up a cell tower or work inside a building.

Display Size: 5″ should be the minimum requirement for a display size; OTDRs with smaller displays cost less but make OTDR trace analysis more difficult.

Battery Life: an OTDR should be usable for a day in the field; 8 hours should be the minimum.

Trace or Results Storage: 128 MB should be the minimum internal memory with options for external storage such as external USB memory sticks.

Bluetooth and/or WiFi Wireless Technology: wireless connectivity enables easily exporting test results to PCs/laptops/tablets.

Modularity/Upgradability: a modular/upgradable platform will more easily match the evolution of your test needs; this may be more costly at the time of purchase but is less expensive in the long term.

Post-Processing Software Availability: although it is possible to edit and document your fibers from the test instrument, it is much easier and more convenient to analyze and document test results using post-processing software.

Before selecting an OTDR, consider the applications that the instrument will be used for and check the OTDR’s specifications to ensure that they are suited to your applications.

 

FIBER-MART.COM OTDR Solution

FIBER-MART.COM OTDRs are available with a variety of fiber types and wavelengths, including single mode fiber, multimode fiber, 1310nm, 1550 nm, 1625 nm, etc. It also supplies OTDRs of famous brands, such as JDSU MTS series, EXFO, YOKOGAWA AQ series and so on. You can find the OTDR best fit your applications in FIBER-MART.COM.