something about optic fiber Splicing

A splice is a device to connect one fiber optic cable to another permanently. It is the attribute of permanence that distinguishes a splice from connectors. Nonetheless, some vendors offer splices that can be disconnected that are not permanent so that they can be disconnected for repairs or rearrangements. The terminology can get confusing.

Fiber optic cables may have to be spliced together for any of a number of reasons. 

One reason is to realize a link of a particular length. The network installer may have in his inventory several fiber optic cables but, none long enough to satisfy the required link length. This may easily arise since cable manufacturers offer cables in limited lengths - usually 1 to 6 km. If a link of 10 km has to be installed this can be done by splicing several together. The installer may then satisfy the distance requirement and not have to buy a new fiber optic cable.

Splices may be required at building entrances, wiring closets, couplers and literally any intermediary point between Transmitter and Receiver. 

At first glance you may think that splicing two fiber optic cables together is like connecting two wires. To the contrary, the requirements for a fiber-optic connection and a wire connection are very different. 

Two copper connectors can be joined by solder or by connectors that have been crimped or soldered to the wires. The purpose is to create an intimate contact between the mated halves in order to have a low resistance path across a junction. On the other hand, connecting two fiber optic cables requires precise alignment of the mated fiber cores or spots in a single-mode fiber optic cable. This is demanded so that nearly all of the light is coupled from one fiber optic cable across a junction to the other fiber optic cable. Actual contact between the fiber optic cables is not even mandatory. The need for precise alignment creates a challenge to a designer of a splice.

There are two principal types of splices: fusion and mechanical.

Fusion splices - uses an electric arc to weld two fiber optic cables together. The splices offer sophisticated, computer controlled alignment of fiber optic cables to achieve losses as low as 0.05 dB. This comes at a high cost.

Mechanical-splices all share common elements. They are easily applied in the field, require little or no tooling and offer losses of about 0.2 dB.

The proper way to store cables

We’ve all experienced it. The crushing dread of pulling out a cable that you need to not only to find that it is a tangled mess but then discover that it no longer works. This can be the nightmare of anyone that works in an industry that relies on wires and cables to help keep equipment working. No matter if you work in audio, video or simply just want cables that you can rely on in order to enjoy media on your devices, having nicely kept cables not only looks great, but can prolong the life of this much needed resource.

One of the big problems with cables is that they can so easily get tangled. Long lengths of wire can be very unwieldy and can be hard to take the time to pack up and secure for future use. Many people who depend on these cords usually do not have the time to devote to standing in one place for long periods of time, wrapping a cord up in their hands. However, the importance of proper cable storage and maintenance should not be underestimated. A properly wrapped cable has the ability to last longer than one that is abused and hastily shoved into a drawer, box or case.

 

Many people are not aware of techniques that can help them save their cables. If a cable is stored improperly or wound the wrong way, it can fray on the inside and can cause damage, leading to the cable malfunctioning. Luckily, learning the proper way to wind and store a cable is very easy. One of the best ways to get started is to simply make a simple loop with the cord in your hand. Then make a loop around in the opposite direction, creating another circle, and coming out in the same place over the fingers again, but inverted. This will reduce the fraying on the inside of the wire and will help prolong the life of the wire. An added benefit is that the cable will not get tangled and all that is needed to unravel it is just to simply start unwinding. The wire will then unravel straight.

However, in order to keep the wire in this form and in order to store it, first leave enough length at the end of the wire in order to thread it through the circle. Then, continue to wrap it around the outside of the circle and through again to the inside, creating a spiral covering the outside of the circle and keeping all of the parts in place.

 

Another great way to wind and store a cable is to start like the above example, but instead of creating a spiral at the end, create a circle at the start and then start a spiral until you run out of wire. This also has the added benefit of shortening the cord so that it takes up less room when in use. Both of the above examples are great ways you can use to help prolong the life of your cables and store them in a quick and easy way.

What Can Limit the Data Transmission Distance?

What Can Limit the Data Transmission Distance?

by Fiber-MART.COM

In the optical network, except the speed, data transmission distance is another important thing that we care. What can limit the transmission distance? At first we may think of fiber optic cable. Compared with copper cable, it can support longer transmission distance, high speed, high bandwidth, etc. However, not everything is perfect. Fiber optic cable still has some imperfections that influence the transmission distance. Besides, other transmitting media like transceivers, splices and connectors can also limit the transmission distance. The following will tell more details.

Fiber Optic Cable Type

Fiber optic cable can be divided into single-mode cable and multimode cable. The transmission distance supported by single-mode cable is longer than multimode cable. That’s because of the dispersion. Usually the transmission distance is influenced by dispersion. Dispersion includes chromatic dispersion and modal dispersion (as shown in the following figures). Chromatic dispersion is the the spreading of the signal over time resulting from the different speeds of light rays. Modal dispersion is the spreading of the signal over time resulting from the different propagation mode.

 

For single-mode fiber cable, it is chromatic dispersion that affects the transmission distance. This is because, the core of the single-mode fiber optic is much smaller than that of multimode fiber. So the transmission distance is longer than multimode fiber cable. For multimode fiber cable, modal dispersion is the main cause. Because of the fiber imperfections, these optical signals cannot arrive simultaneously and there is a delay between the fastest and the slowest modes, which causes the dispersion and limits the performance of multimode fiber cable.

 

Optic Transceiver Module

Like most of the terminals, fiber optic transceiver modules are electronic based. Transceiver modules play the role of EOE conversions (electrics-optics-electrics). The conversion of signals is largely depend on an LED (light emitting diode) or a laser diode inside the transceiver, which is the light source of fiber optic transceiver. The light source can also affect the transmission distance of a fiber optic link.

 

LED diode based transceivers can only support short distances and low data rate transmission. Thus, they cannot satisfy the increasing demand for higher data rate and longer transmission distance. For longer transmission distance and higher data rate, laser diode is used in most of the modern transceivers. The most commonly used laser sources in transceivers are Fabry Perot (FP) laser, Distributed Feedback (DFB) laser and Vertical-Cavity Surface-Emitting (VCSEL) laser. The following chart shows the main characteristics of these light sources.

 

Transmission Frequency

As the above chart mentioned, different laser sources support different frequencies. The maximum distance a fiber optic transmission system can support is affected by the frequency at which the fiber optic signal will be transmitted. Generally the higher the frequency, the longer distance the optical system can support. Thus, choosing the right frequency to transmit optical signals is necessary. Generally, multimode fiber system uses frequencies of 850 nm and 1300 nm, and 1300nm and 1550 nm are standard for single-mode system.

 

Bandwidth

Bandwidth is another important factor that influences the transmission distance. Usually, as the bandwidth increases, the transmission distance decreases proportionally. For instance, a fiber that can support 500 MHz bandwidth at a distance of one kilometer will only be able to support 250 MHz at 2 kilometers and 100 MHz at 5 kilometers. Due to the way in which light passes through them, single-mode fiber has an inherently higher bandwidth than multimode fiber.

 

Splice and Connector

Splice and connector are also the transmission distance decreasing reasons. Signal loss appears when optical signal passes through each splice or connector. The amount of the loss depends on the types, quality and number of connectors and splices.

 

All in all, the above content introduces so many factors limiting the transmission distance, like fiber optic cable type, transceiver module’s light source, transmission frequency, bandwidth, splice and connector. As to these factors, different methods and choices can be taken to increase the transmission distance. Meanwhile, equipment like repeater and optical amplifiers are also useful to support the long distance transmission. So there must be some ways to help you increase the transmission distance.

FTTx PON Insertion Loss Tests

FTTx PON Insertion Loss Tests

by Fiber-MART.COM

Insertion loss tests are primarily used to test FTTx PONs (Passive Optical network) during installation. Insertion loss testing may be performed on individual fiber segments as they’re installed (e.g. test feeder fiber from Central Office  (CO) to Fiber Distribution Hub (FDH), test distribution fiber from FDH to AP, or test drop fiber from AP to subscriber’s home). An end-to-end insertion loss test may also be performed on the FTTx PON after it is partially or fully installed (from CO through feeder fiber, passive splitter, distribution and drop cable to the AP or customer’s premise).

 

A stable optical light source and an optical power meter are required to measure insertion loss. Access to both ends of the fiber-under-test is required. Consequently, this is typically an out-of-service test. To measure loss, received power at the far end of the fiber-under-test must be compared to transmit power injected into the fiber at the near end of the fiber under-test.

 

To simplify loss measurements, the power meter is initially connected to the source with a short patch cable and the source power level is measured and stored as the 0 dB reference level for that wavelength. Since the source’s output power levels and the power meter’s detector response are different at each wavelength, the power meter must be referenced to the source at each test wavelength.

 

Once the source and power meter have been referenced at each of the test wavelengths, the source—with the reference jumper still attached—is connected to one end of the fiber under test. The power meter is connected to the other end of the fiber-under-test. Received power level is measured and displayed. More conveniently, the power meter can compare the received power level to the stored reference, directly displaying optical loss in dB.

 

Simple power meters measure power at only one wavelength at a time. To make loss measurements at multiple wavelengths, the source must be configured for each test wavelength in turn. At the same time, the power meter operator must select the appropriate wavelength at the power meter so the correct detector calibration factor and reference level are applied. This is both time-consuming and error prone, as it requires coordination between the source operator on one end and the power meter user at the other end of the fiber-under-test.

 

To reduce test time and eliminate this potential for errors, FPM3 support twin function, it includes Wave ID. A Wave ID source alternately transmits light at each wavelength. A Wave ID power meter automatically synchronizes to the received wavelengths, eliminating the need for source and power meter to be manually switched between wavelengths.

Guide to Select Waterproof Fiber Optic Patch Cable?

Guide to Select Waterproof Fiber Optic Patch Cable?

by Fiber-MART.COM

Fiber optic waterproof cables are widely used in outdoor applications to connect the major fiber optic lines or receivers or splice enclosures. According to different requirements, both fiber optic patch cords and fiber optic pigtails are available. Water proof fiber cable usually adds a water blocking material between the outer jacket and the inner fiber (or inner jacket) to protect the fiber surface from unwanted damage, such as an armored cable or loose-tube gel-filled cable, or water-tolerable tight-buffered cable. Since there are different types of structure for waterproof cables, is there an easy way to determine which waterproof fiber optic patch cable to choose? In order to help select a right waterproof fiber optic cable quickly, this post will introduce the basic knowledge of waterproof ratings and the features of our waterproof fiber optic cable.

How Is a Waterproof Cable Rated?

Like choosing any other fiber optic patch cables, the connector type, fiber count, fiber type (single-mode or multimode), polish type, cable length and cable jacket are factors that should be considered as well. When buying waterproof fiber optic patch cords, the IP (International Protection or Ingress Protection) rating is an important parameter. Knowing the IP code can help you find your wanted waterproof cable.

IP rating system is a classification showing the degrees of protection from solid objects and liquids. IP rating codes do not include hyphens or spaces, and consist of the letters IP followed by one or two figures. The first number refers to the degree of protection against the entry of foreign solid objects, such as dust. These protection levels range from 0 to 6. The second number of the IP code refers to the degrees of protection against moisture/liquids, which are raging from 0 to 8. The first and second number of the IP code can be replaced by the letter “X” when the protection capacity against solid objects (the first number) or moisture (the second number) has not been tested, for example, IPX7 and IP6X.

Features of fiber-mart.com Waterproof Fiber Optic Patch Cable

fiber-mart.com provides IP67 waterproof fiber optic patch cable, including simplex, duplex, 12 fibers, 24 fibers, and various kinds of connect interfaces are optional, such as LC-LC fiber patch cord, SC-SC fiber patch cord, MPO-MPO fiber patch cord, etc. Other degrees of waterproof fiber optic patch cords can also be customized. Our waterproof fiber patch cables are designed with strong PU jacket and armored structure, which can resist high temperature and fit for harsh environment. Our IP67 waterproof fiber patch cords are featured with high temperature stability and low insertion loss. It is also very convenient to install these waterproof, dust-proof and corrosion-resistant patch cords. The plug and socket design can be used to extend the cable length. They are very suitable for FTTH (fiber to the home) and LAN (local area network) applications.

 

Conclusion

The IP code for waterproof devices is not that difficult to understand and you can get some basic information about the protection degree of a device after you know the meaning of each number. You can use it as a reference in choosing a waterproof cable, but you should also consider other factors according to your specific applications.