The science of fiber optics has its advantages and disadvantages. Though there are more advantages than disadvantages, they still are there. One of the largest disadvantages is the overall price of manufacturing and installation of the fiber optic system. Not only is a large amount of glass wire needed for one of these systems, but expensive transmitters and receivers are needed to move the data it carries. Setting up the wires and splicing them also comes at a large expense and also with a great degree of difficulty.
Fiber optic attenuators 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 attenuators are usually used in two scenarios.
The first case is in fiber optic power level testing. Attenuators 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, attenuators are permanently installed in a fiber optic communication link to properly match transmitter and receiver optical signal levels.
Optical attenuators are typically classified as fixed or variable attenuators.
Fixed attenuators have a fixed optical power reduction number, such as 1dB, 5dB, 10dB, etc.
Variable attenuators’ attenuation level can be adjusted, such as from 0.5 dB to 20dB, or even 50dB. Some variable attenuators 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 attenuators work like a regular adapter. But instead of minimizing insertion loss, it purposely adds some attenuation.
The female to female variable attenuators 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 attenuators work as fiber connectors, you can just plug in your existing fiber connector to its female side.
The in-line patch cable type variable attenuators 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 attenuators. These instrument type attenuators 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.
Source: fiber optic cable manufacturer
In fiber optics technology singlemode fiber is one of two types of fiber currently in use. It is a single strand of glass fiber for a single ray (or mode) of light transmission. Singlemode fiber is used for long distance transmission.
Compare with multimode fiber
Source: fiber optic patch cord
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In fiber optics technology multimode fiber cable is used for signal transmission over short distances. In multimode fiber light waves are dispersed into numerous paths as they travel through the cable’s core.
Source: fiber optic cables
JiaFu® is internationally recognized for pioneering the design and production of fiber optic cables for the most demanding military field applications, as well as of fiber optic cables suitable for both indoor and outdoor use, and creating a broad product offering built on the evolution of these fundamental technologies. OCC also is internationally recognized for its role in establishing copper connectivity data communications standards, through its innovative and patented technologies.
Founded in 2001, Jfiberoptic is headquartered in Roanoke, Virginia with offices, manufacturing and warehouse facilities located in each of Roanoke, Virginia, near Asheville, North Carolina and near Dallas, Texas. OCC’s facilities are ISO 9001:2008 registered, and OCC’s Roanoke and Dallas facilities are MIL-STD-790F certified.
Optical Cable Corporation, Jfiberoptic, Procyon, Superior Modular Products, SMP Data Communications, Applied Optical Systems, and associated logos are trademarks of Optical Cable Corporation.
Further information about Jfiberoptic® is available at www.jfiberoptic.com.
This news release by Optical Cable Corporation and its subsidiaries (collectively, the “Company” or “OCC”) may contain certain forward-looking information within the meaning of the federal securities laws. The forward-looking information may include, among other information, (i) statements concerning our outlook for the future, (ii) statements of belief, anticipation or expectation, (iii) future plans, strategies or anticipated events, and (iv) similar information and statements concerning matters that are not historical facts. Such forward-looking information is subject to known and unknown variables, uncertainties, contingencies and risks that may cause actual events or results to differ materially from our expectations, and such known and unknown variables, uncertainties, contingencies and risks may also adversely affect Optical Cable Corporation and its subsidiaries, the Company’s future results of operations and future financial condition, and/or the future equity value of the Company. A partial list of such variables, uncertainties, contingencies and risks that could cause or contribute to such differences from our expectations or that could otherwise adversely affect Optical Cable Corporation and its subsidiaries is set forth in Optical Cable Corporation’s quarterly and annual reports filed with the Securities and Exchange Commission (“SEC”) under the heading “Forward-Looking Information.” Jfiberoptic’s quarterly and annual reports are available to the public on the SEC’s website at http://www.sec.gov. In providing forward-looking information, the Company expressly disclaims any obligation to update this information, whether as a result of new information, future events or otherwise except as required by applicable laws and regulations.
Understanding the characteristics of different fiber optic cables types aides in understanding the applications for which they are used. Operating a fiber optic system properly relies on knowing what type of fiber is being used and why. There are two basic types of fiber cables: multimode fiber optic cable and single-mode fiber optic cable. 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.
Multimode fiber cables, the first to be manufactured and commercialized, simply refers to the fact that numerous modes or light rays are carried simultaneously through the waveguide. Modes result from the fact that light will only propagate in the fiber core at discrete angles within the cone of acceptance. This fiber type has a much larger core diameter, compared to single-mode fiber, allowing for the larger number of modes, and multimode fiber is easier to couple than single-mode optical fiber. Multimode fiber may be categorized as step-index or graded-index fiber. Multimode Step-index Fiber Figure 2 shows how the principle of total internal reflection applies to multimode step-index fiber. Because the core’s index of refraction is higher than the cladding’s index of refraction, the light that enters at less than the critical angle is guided along the fiber.
Three different lightwaves travel down the fiber. One mode travels straight down the center of the core. A second mode travels at a steep angle and bounces back and forth by total internal reflection. The third mode exceeds the critical angle and refracts into the cladding. Intuitively, it can be seen that the second mode travels a longer distance than the first mode, causing the two modes to arrive at separate times. This disparity between arrival times of the different light rays is known as dispersion, and the result is a muddied signal at the receiving end. For a more detailed discussion of dispersion, see “Dispersion in Fiber Optic Systems” however, it is important to note that high dispersion is an unavoidable characteristic of multimode step-index fiber. Multimode Graded-index Fiber Graded-index refers to the fact that the refractive index of the core gradually decreases farther from the center of the core. The increased refraction in the center of the core slows the speed of some light rays, allowing all the light rays to reach the receiving end at approximately the same time, reducing dispersion.Figure 3 shows the principle of multimode graded-index fiber. The core’s central refractive index, nA, is greater than that of the outer core’s refractive index, nB. As discussed earlier, the core’s refractive index is parabolic, being higher at the center. As Figure 3 shows, the light rays no longer follow straight lines; they follow a serpentine path being gradually bent back toward the center by the continuously declining refractive index. This reduces the arrival time disparity because all modes arrive at about the same time. The modes traveling in a straight line are in a higher refractive index, so they travel slower than the serpentine modes. These travel farther but move faster in the lower refractive index of the outer core region.
Single-mode fiber allows for a higher capacity to transmit information because it can retain the fidelity of each light pulse over longer distances, and it exhibits no dispersion caused by multiple modes. Single-mode fiber also enjoys lower fiber attenuation than multimode fiber. Thus, more information can be transmitted per unit of time. Like multimode fiber, early single-mode fiber was generally characterized as step-index fiber meaning the refractive index of the fiber core is a step above that of the cladding rather than graduated as it is in graded-index fiber. Modern single-mode fibers have evolved into more complex designs such as matched clad, depressed clad and other exotic structures.
Single-mode fiber has disadvantages. The smaller core diameter makes coupling light into the core more difficult. The tolerances for single-mode connectors and splices are also much more demanding. Single-mode fiber has gone through a continuing evolution for several decades now. As a result, there are three basic classes of single-mode fiber used in modern telecommunications systems. The oldest and most widely deployed type is non dispersion-shifted fiber(NDSF). These fibers were initially intended for use near 1310 nm. Later, 1550 nm systems made NDSF fiber undesirable due to its very high dispersion at the 1550 nm wavelength. To address this shortcoming, fiber manufacturers developed, dispersion-shifted fiber(DSF), that moved the zero-dispersion point to the 1550 nm region. Years later, scientists would discover that while DSF worked extremely well with a single 1550 nm wavelength, it exhibits serious nonlinearities when multiple, closely-spaced wavelengths in the 1550 nm were transmitted in DWDM systems. Recently, to address the problem of nonlinearities, a new class of fibers were introduced. These are classified as non zero-dispersion-shifted fibers (NZ-DSF). The fiber is available in both positive and negative dispersion varieties and is rapidly becoming the fiber of choice in new fiber deployment. For more information on this loss mechanism, see the article “Fiber Dispersion.”
One additional important variety of single-mode fiber is polarization-maintaining (PM) fiber. All other single-mode fibers discussed so far have been capable of carrying randomly polarized light. PM fiber is designed to propagate only one polarization of the input light. This is important for components such as external modulators that require a polarized light input. Figure 7 shows the cross-section of a type of PM fiber. This fiber contains a feature not seen in other fiber types. Besides the core, there are two additional circles called stress rods. As their name implies, these stress rods create stress in the core of the fiber such that the transmission of only one polarization plane of light is favored. Single-mode fibers experience nonlinearities that can greatly affect system performance.
Loss budget analysis is the calculation and verification of a fiber optic system’s operating characteristics. This encompasses items such as routing, electronics, wavelengths, fiber type, and circuit length. Attenuation and bandwidth are the key parameters for budget loss analysis.
Analyze Fiber Optic Link Loss In The Design Stage
Prior to designing or installing a fiber optic system, a loss budget analysis is reccommended to make certain the system will work over the proposed link. Both the passive and active components of the circuit have to be included in the budget loss calculation. Passive loss is made up of fiber loss, connector loss, and splice loss. Don’t forget any couplers or splitters in the link. Active components are system gain, wavelength, transmitter power, receiver sensitivity, and dynamic range. Prior to system turn up, test the circuit with a source and FO power meter to ensure that it is within the loss budget.
The idea of a loss budget is to insure the network equipment will work over the installed fiber optic link. It is normal to be conservative over the specifications! Don’t use the best possible specs for fiber attenuation or connector loss – give yourself some margin!
The best way to illustrate calculating a loss budget is to show how it’s done for a 2 km multimode link with 5 connections (2 connectors at each end and 3 connections at fiber optic patch panels in the link) and one splice in the middle. See the drawings below of the link layout and the instantaneous power in the link at any point along it’s length, scaled exactly to the link drawing above it.
Fiber Optic Cable Plant Passive Component Loss
Step 1. Fiber loss at the operating wavelength
|Fiber Atten. dB/km||3 [3.5]||1 [1.5]||0.4 [1/0.5]||0.3 [1/0.5]|
|Total Fiber Loss||6.0 [7.0]||2.0 [3.0]|
Step 2. Connector Loss
Multimode connectors will have losses of 0.2-0.5 dB typically. Singlemode connectors, which are factory made and fusion spliced on will have losses of 0.1-0.2 dB. Field terminated singlemode connectors may have losses as high as 0.5-1.0 dB. Let’s calculate it at both typical and worst case values.
|Connector Loss||0.3 dB (typical adhesive/polish conn)||0.75 dB (TIA-568 max acceptable)|
|Total # of Connectors||5||5|
|Total Connector Loss||1.5 dB||3.75 dB|
(All connectors are allowed 0.75 max per EIA/TIA 568 standard)
Step 3. Splice Loss
Multimode splices are usually made with mechanical splices, although some fusion splicing is used. The larger core and multiple layers make fusion splicing abut the same loss as mechanical splicing, but fusion is more reliable in adverse environments. Figure 0.1-0.5 dB for multimode splices, 0.3 being a good average for an experienced installer. Fusion splicing of singlemode fiber will typically have less than 0.05 dB (that’s right, less than a tenth of a dB!)
|Typical Splice Loss||0.3 dB|
|Total # splices||1|
|Total Splice Loss||0.3 dB|
(All splices are allowed 0.3 max per EIA/TIA 568 standard)
Step 4. Total Passive System Attenuation
Add the fiber loss, connector and splice losses to get the link loss.
|Best Case||TIA 568 Max|
|850 nm||1300 nm||850 nm||1300 nm|
|Total Fiber Loss (dB)||6.0||2.0||7.0||3.0|
|Total Connector Loss (dB)||1.5||1.5||3.75||3.75|
|Total Splice Loss (dB)||0.3||0.3||0.3||0.3|
|Total Link Loss (dB)||7.8||3.8||11.05||7.05|
Remember these should be the criteria for testing. Allow +/- 0.2 -0.5 dB for measurement uncertainty and that becomes your pass/fail criterion.
Equipment Link Loss Budget Calculation: Link loss budget for network hardware depends on the dynamic range, the difference between the sensitivity of the receiver and the output of the source into the fiber. You need some margin for system degradation over time or environment, so subtract that margin (as much as 3dB) to get the loss budget for the link.
Step 5. Data From Manufacturer’s Specification for Active Components (Typical 100 Mb/s link)
|Operating Wavelength (nm)||1300|
|Receiver Sens. (dBm@ required BER)||-31|
|Average Transmitter Output (dBm)||-16|
|Dynamic Range (dB)||15|
|Recommended Excess Margin (dB)||3|
Step 6. Loss Margin Calculation
|Dynamic Range (dB) (above)||15||15|
|Cable Plant Link Loss (dB)||3.8 (Typ)||7.05 (TIA)|
|Link Loss Margin (dB)||11.2||7.95|
As a general rule, the Link Loss Margin should be greater than approximately 3 dB to allow for link degradation over time. LEDs in the transmitter may age and lose power, connectors or splices may degrade or connectors may get dirty if opened for rerouting or testing. If cables are accidentally cut, excess margin will be needed to accommodate splices for restoration.
Source: http://www.jfiberoptic.com, fiber optic cables
OVUM latest market data shows, 100G optical network equipment sales for the year for the first time exceeded $ 1 billion. However, optical networking equipment from 2013Q1 overall sales results, the growth of the market still faces challenges.
“A quarter of the market decline is very common, but this decline is still worrying, because this is compared with the same quarter of the fifth time since the fall, and the lowest quarterly revenue as six years.” Ovum network infrastructure analysis division Ron Kline expressed.
However, Kline is not entirely an expected sadly. “Bright side is, 100G continues to show strong growth with the ring than in 2013 a quarter of 100G port shipments increased 41% QoQ revenue growth of 24%, with annual revenues for the first time more than one billion U.S. dollars. 2013Q1 have 20 devices equipment providers earn income in 100G, more vendors will enter the market this year. forecast from equipment manufacturers cautiously optimistic, orders increased short-term visibility is good, but the long-term visibility is also shrouded in clouds. ”
Ovum recently released market share analysis shows that the next generation of optical packet transmission system integration sales, including OTN switching equipment, an increase of the same quarter last year, performed well. However, 40G equipment first decline in annual sales, which may indicate that with the rapid decline in equipment prices 100G, 40G market is beginning to decline. From a regional perspective, compared to the same quarter last year, the Asia Pacific and EMEA expenses decreased, spending was flat in North America, South American growth of 15%.
The current downturn comes to non-IP / Ethernet aggregation equipment expenses increased significantly slow the growth of the European economy and fierce competition led to lower prices.
Overall, the optical network equipment market outlook is brighter edges.
In early May, finance chair Kathy Sertich said it was bad timing to pay for the installation of fiber optic from the school district. Now, it seems there is no time like the present.
The Mayville Common Council approved Monday evening an agreement with the Mayville School District to run fiber optic cable to City Hall to allow the police department to have high-speed access to security cameras at the schools with no cost to the city.
“The school district of Mayville proposes to install six strands of fiber to the city of Mayville as part of the district’s infrastructure upgrade at the school district’s cost,” said Sue Wery, technology director for the district.
Only two of those strands will be used at this time to allow police to connect to the cameras. The other four will be built in for future expansion at City Hall. The city will also not have to pay for any equipment needed for monitoring. The installation is slated for July/August.
“I think this is a great thing and I am glad,” Sertich said. “Thank you, because at this point we could not do it with the deficit that we’re still covering.”
On May 8, the city held a meeting in which it was determined that a fiber optic tie-in was not financially feasible due to a strict nine-year plan to pull the city out of debt. It was estimated to cost $5,800.
On May 22, the district was put on lockdown during a weapons scare which highlighted some shortcomings in the security plan. On June 11, the Wisconsin Board of Commissioners of Public Lands approved a $225,000 loan to the district for the project.
Wery said that hopefully next year they can apply for another grant that would reimburse them for the cost of the tie in as well as getting more cameras in the future.
“We didn’t want to incur any additional charges for you to have to come back next year and do it,” said John Westphal, school board president.
Source: fiber optic connectors
Furthermore, the 2013 Hurricane Season began on June 1, and the National Oceanic and Atmospheric Association expects it to be a busy period. With climate change continuing in much of the world and many experts anticipating extreme storms becoming more common moving forward, there is a growing need to construct buildings to the highest standards for safety. Meeting building codes that help a structure withstand extreme weather can save lives, and fiber cables play a vital role in this process.
There are two key perspectives to keep in mind when it comes to cabling and network equipment architectures in areas often impacted by natural disasters – maintaining communication and allowing free movement.
Cabling architectures and communication availability
Ensuring communications remain available is vital during a disaster. If workers in the office lose the internet because of a tornado, the business disruption is a problem, but not nearly as much of an issue as it would be if communications go down completely. Installing cabling architectures that interconnect with telecom infrastructure is a key part of a construction process, and how these systems are deployed can impact communications availability during a disaster. Having alternative network options that can provide emergency communications can also help, ensuring that emergency services can be contacted in the event of a disaster event.
Installing cables to ensure free movement through a building
A poor cabling setup can lead to major problems when disasters strike. Loose wires can clump together, blocking doors, hallways and other areas, preventing people from getting out of a building to escape or into a structure to rescue any trapped individuals. Meeting high standards for safety, including regulations from OSHA and national fire codes can provide a solid foundation for safe and well-designed cable deployment. However, it is important to also consider the quality of the components that keep cables in place and how the wiring systems are laid out in the building to ensure they do not become obstructions during a disaster.
Cabling installation methods could mean the difference between life and death during a disaster. When a tornado or hurricane hits an area, employees must be able to get to safety, or get help, as quickly as possible. Cables that get in the way can be a detriment to this process, but a well-designed system will not only stay out of the way, it could help keep key communication channels available.