Category: Fiber Transceivers

Every broadband installer should know about the different types of fiber networks. The two main ones are: point-to-point and passive optical network (PON).

Think of how a phone call works and you’ll get the gist of a point-to-point network. There’s a direct connection between two phones, or nodes, and the other phone only hears the call.

A PON, in contrast, is a point-to-multipoint network where a signal is shared.

In the case of fiber optic networks, the point-to-point architecture would involve a switch at the central office of the Internet Service Provider (ISP) connected by multi-fiber cable to an aggregation switch in a cabinet on the street.

These switches have multiple optical ports – each of which is connected by fiber to an optical network termination or ONT in an enclosure somewhere on or near the building. These connections are dedicated and full duplex, meaning that the download and upload speed and bandwidth are the same.

As the point-to-point architecture features dedicated fiber, it’s also able to deal with higher capacity and technology changes down the road.

HOW NETWORK TYPES AFFECT FIBER PRICING

Guess why a PON is a cheaper option? There’s a lot less fiber needed than a point-to-point network. The central office would have an optical line terminal (OLT), which connects by multi-fiber to a series of passive optical splitters that divide the signal up to 64 times! This reduces costs by sharing components including an expensive laser with multiple premises. The return data can be sent using a cheaper laser as the bandwidth is less and the splitter is bidirectional.

Sounds great, but there’s a drawback with this type of network: the bandwidth is shared so speed is limited. Also, download speeds are much higher than upload speeds, which can be a problem with video conferencing and file sharing.

The optical line terminal converts the signal from the ISP’s fiber backbone and also receives the uploaded data from the customer. The passive splitter divides the light signal into two or more signals. It is usually located somewhere fairly close to the customer so as to reduce the amount of fiber required. A 1 to 64 split ratio is common and can be achieved by combining different combinations of splitter. For example, a four way splitter can connect to another splitter located closer to the premises that splits the signal again into sixteen feeds. This saves running so much fiber back to the first splitter.

As fiber continues to be rolled out to cities across North America, it’s a good idea get familiar with the different types of PONs.

-Broadcast PON or BPON was the original method and used the standard telephone network protocol ATM or asynchronous transfer mode.

-Ethernet PON or EPON uses the IEEE Ethernet standard and is capable of 1 Gbps.

-Gigabit capable PON or GPON uses Internet protocol or IP and handles data up to 2.5 Gbps downstream and 1.5 Gbps upstream. It is also triple play, which means it can handle voice, data and video. It is the system most planned fiber to the premises (FTTP) will use. However, bandwidth requirements have already exceeded this standard so work is being done to improve it.

-A new standard NGPON2 is being developed that will be capable of 40 Gbps downstream and 10 Gbps upstream with the potential of those being doubled.

What is a fiber optic fusion splicer?

A fiber optic fusion splicer is a device that uses an electric arc to melt two optical fibers together at their end faces, to form a single long fiber. The resulting joint, or fusion splice, permanently joins the two glass fibers end to end, so that optical light signals can pass from one fiber into the other with very little loss.

How does a fusion splicer work?

Before optical fibers can be successfully fusion-spliced, they need to be carefully stripped of their outer jackets and polymer coating, thoroughly cleaned, and then precisely cleaved to form smooth, perpendicular end faces. Once all of this has been completed, each fiber is placed into a holder in the splicer’s enclosure. From this point on, the fiber optic fusion splicer takes over the rest of the process, which involves 3 steps:

Alignment: Using small, precise motors, the fusion splicer makes minute adjustments to the fibers’ positions until they’re properly aligned, so the finished splice will be as seamless and attenuation-free as possible. During the alignment process, the fiber optic technician is able to view the fiber alignment, thanks to magnification by optical power meter, video camera, or viewing scope.

Impurity Burn-Off: Since the slightest trace of dust or other impurities can wreak havoc on a splice’s ability to transmit optical signals, you can never be too clean when it comes to fusion splicing. Even though fibers are hand-cleaned before being inserted into the splicing device, many fusion splicers incorporate an extra precautionary cleaning step into the process: prior to fusing, they generate a small spark between the fiber ends to burn off any remaining dust or moisture.

Fusion: After fibers have been properly positioned and any remaining moisture and dust have been burned off, it’s time to fuse the fibers ends together to form a permanent splice. The splicer emits a second, larger spark that melts the optical fiber end faces without causing the fibers’ cladding and molten glass core to run together (keeping the cladding and core separate is vital for a good splice – it minimizes optical loss). The melted fiber tips are then joined together, forming the final fusion splice. Estimated splice-loss tests are then performed, with most fiber fusion splices showing a typical optical loss of 0.1 dB or less.

This paper explores using fiber optic cabling and sensors to achieve cost-effective, long-distance intrusion monitoring.  Also covered are the advantages of these non-electric, spark-free fiber optic sensors, which enable their use in chemical plants, underground installations and other environments where explosive gases may be present.

Background

The telecommunications industry has long known the advantages of using optical fiber to send information over great distances. Now the security industry has the opportunity to use the same technology to achieve long distance intrusion monitoring using the same technology and components as that used in a telecommunications network.

It must be recognized that using fiber optics in security applications is not a new idea. Security systems exist that use specialized, highly sensitive optical fiber involving doped fiber cladding and interferomic sensing equipment.

These highly sensitive security systems are not the subject of this paper. These systems are excellent for monitoring small areas, but they are not usually deployed to monitor distances greater than 1000 feet, such as the perimeter around an airport or large factory complex.  These systems are too expensive for such large-scale deployment, and they are so sensitive they can be subject to frequent nuisance alarms caused by environmental factors when monitoring large areas.

Instead, this paper focuses a new technique of applying common, low-cost optical fiber to monitor large-scale facilities.

A Cost-Effective Approach

This new approach takes advantage of optical fiber’s sensitivity to optical losses resulting from “macrobending,” i.e. bending fiber to a radius of curvature that is tight enough to produce measurable light loss.  Because this approach uses standard communication optical fiber, the tools, installation and maintenance of this type of security system is no different than that required for a standard fiber optic telecommunications link.

Actually, this technology has been used in communication closets for years to signal an alert if a fiber optic cable in a large network becomes broken, severely bent, or is otherwise damaged.

  For example, if a backhoe operator were to accidentally break a buried fiber optic telecommunications cable, repair personnel are alerted. They then use a device called an Optical Time Domain Reflectometer (OTDR) to identify the type of problem and pinpoint exactly where it occurred along many miles of cable.

  An OTDR is required to average thousands of reflections at intervals along the fiber to identify this break point, typically requiring 10 seconds or more to complete the process.

This inherent ability of fiber optic technology to pinpoint the location of a bent or broken cable makes this same technology ideal for pinpointing the location of an intruder. For example, if an intruder breaks or bends an optical fiber that has been installed around the perimeter of a facility, the location of their intrusion attempt can be pinpointed with an OTDR that is built into the system.

  One minor problem in using this approach in a security application is that for an OTDR to detect a measurable amount of optical loss, the optical fiber must either be broken or bent at a relatively sharp angle.  In most cases, an intruder would likely bend the cable only slightly to gain access to a protected facility; the light loss produced by this slight bend would not be enough to be detected by the OTDR.

  Fortunately, the solution is straightforward.  It involves installing simple spring-loaded triggering devices along the cable route that can sense a slight disturbance to the perimeter cable, and then magnify that disturbance by creating a much more pronounced bend in the cable. This tighter bend produces enough light loss to be detected by the OTDR.

  Example # 1 – Perimeter Security

In this first example, standard fiber optic cable (with a U.V. resistant jacket) is attached to the existing fencing around a perimeter of a large facility, such as a military base. The fiber is held in place by a number of triggering devices installed on the fencing at intervals around the perimeter.

A laser injects infrared light into one end of the fiber optic cable and the light is continually monitored with the system’s built-in OTDR to determine if there has been any change in light output. If the fiber optic cable is broken, or one of the trigger devices is activated by a slight disturbance to the cable, the system triggers an alarm.

The triggering devices installed along the perimeter can include mechanical adjustments to control their level of sensitivity. System sensitivity can also be adjusted by varying the wavelength of the injected infrared light.

Example # 2 – Security for Underground Facilities

In a similar example, the fiber optic cable is attached beneath a number of manhole covers, to protect against unauthorized access to underground utilities.

An opto-magnetic triggering device is installed beneath each manhole cover.  When one of these devices sense that a manhole cover has been removed, it triggers an internal mechanism that creates a tight bend in the fiber. As in the first example, the OTDR at the head end of the system senses the resulting loss of light, triggers an alert, and pinpoints the exact location of the event.

Problems Solved

This new approach provides solutions to some of the classic challenges faced by security system designers, such as:

How to monitor very large distances in a cost-effective manner?

Fiber carries signals over a much greater distance than copper wire without requiring re-amplification of the signal. With fiber, no electrical source is required to power the sensors. This makes fiber optics a cost-effective security solution for monitoring very large perimeters, such as those around military bases, large factory complexes, and so forth.

How to reduce the greater incidence of nuisance alarms that result when monitoring large areas?

The perimeter monitoring approach discussed here involves using opto-mechanical sensors that include mechanisms that allow for tension adjustments of the fiber optic sensing cable. The sensors can be adjusted to resist wind, snow and other environmental factors to reduce or even eliminate nuisance alarms. Varying the wavelength of the light injected into the cable can also adjust the sensitivity of the system.

How to guard against someone defeating the security system?

A unique attribute of a fiber optic security system is that, unlike copper wire,  optical fiber cannot be cut, spliced into, or jumped without being detected.

How to monitor environments subject to explosive gases? Fiber optics use infrared light, not electricity, to transmit signals.  Unlike copper wire, optical fiber cannot arc or produce a spark that could trigger an explosion. This makes fiber optic sensors ideal for monitoring chemical plants, underground installations, storage tanks and many other areas where combustible gases may be present.

How to monitor environments where there are conductive or corrosive liquids or gases?

Optical fiber is made of glass, which is inert.  Unlike metallic wire, optical fiber will not corrode when subject to chemicals, and it cannot short out, even when exposed to water.

How to design a system that can survive electrical storms?

A security system that covers a wide area is more subject to damage or destruction caused by lightning storms. Optical fiber, which is glass, does not conduct electricity or lightning.  If one sensor is destroyed by a lightning strike, the lightning cannot travel over the optical cable to destroy other sensors and components within the system.

Installation Considerations

As one might conclude, security systems that use light (photons) instead of electricity (electrons) require a different skill set as far as security installers are concerned. The handling of fiber optics is not necessarily more difficult, but it does require some new knowledge and tools.

Fiber optic security systems as described above would also require a user-friendly software program to integrate the system’s OTDR with a display monitor to show tripped sensors along the cable run. Carefully labeled visual maps, showing the attenuation locations, would enable the security guard to quickly locate an intrusion attempt and provide a quick response.

As mentioned earlier, there are different types of fiber optic security systems. Installers must be familiar with the particular type of fiber optic system specified by the end user as well as the installation specifications required by the manufacturer of the system.  Only factory trained and authorized installers should attempt installation of fiber optic security systems.

A single optical fiber can carry a huge amount of bandwidth using Time-Division Multiplexing (TDM) and Coarse Wavelength Division Multiplexing (CWDM), which may be combined.

TDM was developed for digital telephony to send independent signals over a single fiber using synchronized switches at each end so that each signal appears on the line in short bursts, creating an alternating pattern. For audio/video, it is more efficient to convert any analog signals into digital and then combine them into one data stream using TDM.

CWDM was developed for the broadcast industry to combine signals from different bands onto a single fiber, using the wavelengths from 1270 nm through 1610 nm with a channel spacing of 20 nm (technically, it was shifted by 1 nm to 1271 to 1611 nm). Channel spacing ensures that minor signal drifting will not contribute to crosstalk or otherwise affect different wavelengths negatively, as well as, permits the usage of less sophisticated transceiver designs, thus contributing to a reduction in cost.

To understand how CWDM works, we need to first understand how fiber signal transport makes use different wavelengths (colors) of laser light in the infrared zone, which is 700 nm to 1 mm (1,000,000 nm), to carry different signals.

The earliest fiber systems operated in the first band, 850 nm, which are shorter wavelengths best suited for multimode fiber. The bands or “optical windows” are regions within the optical fiber spectrum with low optical loss (“attenuation”). The second band is 1310 nm, which has a longer wavelength and is used by both multimode and singlemode fiber with zero dispersion, and the third band is 1550 nm, which is an even longer wavelength and is used exclusively by singlemode fiber. Optical loss or attenuation can vary depending on whether the fibers are plastic or glass, and which wavelengths are being used.

A CWDM system uses a multiplexer at the source to combine or “muxes” the signals, and a demultiplexer at the destination “demuxes” them to split them apart again. Some units can both multiplex and demultiplex simultaneously, which is called an “add-drop multiplexer,” combining the functionality into one.

Benefits of CWDM

The main advantage of CWDM is that it allows companies to expand their network capacity without laying more fiber. In a CWDM configuration, the capacity of a fiber link can be expanded simply by adding or upgrading the multiplexers and demultiplexers at both ends. With CWDM it is possible to carry the combined video/audio/data information from an entire equipment rack on just one fiber.

When this technology was originally developed in the 70s and 80s it was somewhat cost-prohibitive, but over time CWDM multiplexing has undergone considerable refinement even as costs have come down, so more companies can afford to use it. CWDM multiplexing is particularly popular in countries with limited infrastructures, where it is highly desirable to maximize usage of all installed fiber optic cabling.

One of the most significant benefits of CWDM is that you can use off-the-shelf Small Form-Factor Pluggables (SFPs). SFPs are optical transceivers for specific wavelengths and they are hot-swappable: if one should fail, you can easily substitute another one, and it will work as long as the data rate matches the same standard as the one being replaced.

Multimode vs. Singlemode Fiber

Multimode fiber is utilized between points that are a short distance apart, such as within the same building. The most common wavelengths used for multimode fiber are 850 nm and 1310 nm, with each wavelength going in different directions in the fiber, and also is ideally supported by CWDM multiplexing.

Telephony network designers were the first to take advantage of multimode fiber but by the early 1980s singlemode fiber, which can be run for much longer distances, began operating in the 1310 nm wavelength and later in the 1550 nm wavelength, so it became the more widely accepted standard.

Singlemode fiber continued to improve and now has a usable spectrum from about 1270 nm to 1610 nm. Since fiber can handle up to 8 channels of video per wavelength, and can have up to 18 CWDM wavelengths on one fiber, this means that more than 144 channels of video can be transported over one fiber! This makes fiber the unparalleled solution for high-bandwidth video transport. Other advantages of fiber include its light-weight cables as compared to copper, its immunity to lightning, EMI/RFI and crosstalk, and its increased security as it can’t be “tapped” like copper. Singlemode fiber is also less fragile than multimode fiber, allowing Installers to more easily handle it.

Optiva Fiber System

fiber-mart’s Optiva fiber system was designed to take advantage of TDM and CWDM technologies, to maximize the use of fiber lines and the signals handled per insert card. Many signals can be daisy-chained together, allowing additional signals to be added without adding additional fiber, or can be multiplexed onto a single fiber.

While most Optiva insert cards allow for CWDM multiplexing, it really depends how much bandwidth the signal being sent requires and what SFPs are being used in the transmitter/receiver cards, in order to determine the maximum distance capability, whether multimode or singlemode fiber is usable, and whether a single fiber (“simplex”) or 2 fibers (“duplex”) is needed to complete the system. As SFPs have evolved to handle increased bandwidth, the most commonly used ones are 2.97 Gbps (aka 3 Gbps), 4.25 Gbps, and 10 Gbps, the latter of which are called SFP+.

Optiva additionally has separate CWDM passive optical multiplexer/demultiplexer insert cards for 4-channels (MDM-7004), 8-channels (MDM-7008), or 16-channels (MDM-7016), designed to send or receive up to 4, 8, or 16 individual signals respectively, with bandwidths up to 3.125 Gbps per wavelength.

In optical fiber communications, a WDM transponder is a common element that sends and receives the optical signal from a fiber. Maybe you have seen and used it many times. But do you really know it clearly? How much do you know? Today, this article is going to talk about something about WDM (Wavelength Division Multiplexing) transponder.

What’s WDM Transponder?

WDM transponder, also named as fiber optic transponder, is an optical-electrical-optical (OEO) wavelength converter which is designed to perform an O-E-O operation to convert wavelengths of light. It plays a key role in WDM system, especially in DWDM (Dense Wavelength Division Multiplexing) system. Its name “transponder” is short for transmitter and responder, which clearly show its purpose. They are protocol and rate-transparent fiber media converters that support SFP, SFP+, XFP and QSFP transceivers with data rates up to 11.32 Gpbs. WDM transponders extend network distance by converting wavelengths (1310 to 1550nm), amplifying optical power and can support the “Three Rs” to Retime, Regenerate and Reshape the optical signals. In general, there is an O-E-O (optical-electrical-optical) function with this device. Fiber optic transponders and optical multiplexers are usually present in the terminal multiplexer.

How does the WDM Transponder work?

The most distinguished characteristic of WDM transponder is that it can automatically receive, amplify, and then retransmit a signal on a different wavelength without altering the data/signal content. In today’s commercial networks, wavelength conversion is only realized with optical to electronic to optical (O-E-O) transponders. OEO Transponder works as a regenerator which converts an optical input signal into electrical form, generates a logical copy of an input signal with a new amplitude and shape of its electrical pulses and uses this signal to drive a transmitter to generate an optical signal at the new wavelength. Here is a picture showing how a transponder works. From left to right, the transponder receives an optical bit stream operating at one particular wavelength (1310 nm). And then it converts the operating wavelength of the incoming bitstream to an ITU-compliant wavelength and transmits its output into a DWDM system. On the receive side (right to left), the process is reversed. The transponder receives an ITU-compliant bit stream and converts the signals back to the wavelength used by the client device.

What’s the Major Functions of WDM Transponder?

WDM transponder is a vital element in optical communication. Usually, its major function includes:

Conversions between electrical and optical signals

Serialization and deserialization

Why WDM Transponder Is Needed in WDM System?

There are several reasons that we need wavelength-converting transponder. The first reason is that they can connect incompatible equipment. Such an example is the conversion of 1300nm carrying wavelength of optic networks. Another one is because we have different fiber optic networks with different providers and different criteria. Therefore, we need WDM transponder to traverse from one fiber network to another. WDM transponder helps us to reduce the number of wavelengths required.

How Many Applications of WDM Transponder Do You Know?

WDM transponders are widely used in a number of networks and applications. The following are their major applications.

Convert Multimode to Single-Mode Fiber

It’s known to us that multimode fiber is often used for short distance transmission while single-mode fiber is used for long distance transmission. In order to exceed the limitation of multimode fibers, mode conversion is needed in networks. As the following figure showing, two switches are connected by the WDM transponder which convert the multimode fibers to single-mode fibers.

Convert Dual Fiber to Single-Fiber

In this case, two dual fiber switches are connected with a single-fiber via two transponders. The single fiber uses 1310nm and 1550nm wavelengths over the same fiber strand in opposite directions. As the following figure showing.

Wavelengths Conversion

The most common application of WDM transponder is wavelengths conversion. Fiber optic communications equipment with fixed fiber interfaces (ST, SC, LC or MTRJ connectors) operating over legacy wavelengths (850nm, 1310nm, 1550nm) must be converted to CWDM wavelengths with a transponder. In this application, the transponder is called WDM transponder or wavelength-converting transponder.

In addition, WDM transponder also can be used to extend 10G OTN network distances, SONET ring distances and provide a standard line interface for multiple protocols through replaceable 10G small form-factor pluggable (XFP) client-side optics.

Conclusion

With its own special features, WDM transponder facilitates a wide application in optical networks. Fiberstore provides a number of choices for OEO WDM transponder which have high performance and good quality. Here you can find different transmission rates of this products such as 2.5G, 4.25G, 8G, 10G and 40G, and different ports of OEO converters such as SFP+ to SFP+, SFP+ to XFP, XFP to XFP, etc. If you want to know more, please visit fiber-mart.COM.

MPO—Multi-fiber Push On—is a type of optical connector that has been the primary multiple fiber connector for high-speed telecom and data communications networks. It has been standardized within the IEC 61754-7 and TIA 604-5. This connector and cabling system first supported telecommunications systems especially in the Central and Branch offices. Later it became the primary connectivity used in HPC or high-performance computing labs and enterprise datacenters. It has also been heavily used in cloud datacenters but is now being replaced with the lower cost MXC optical connector and cabling systems because of a much more controlled, benign environment versus the rugged Telcordia testing and validation requirements.

Over the years, the MPO connector family has evolved to support a wider range of applications and system packaging requirements. Now there are several more suppliers investing and developing products with new features and fiber counts. Originally a single row 12-fiber connector, there are now 8 and 16 single row fiber types that can be stacked together to form 24, 36 and 72 fiber connectors using multiple precision ferrules. However, the wider row and stacked ferrules have had insertion loss and reflection issues due to the difficulty of holding alignment tolerances on the outer fibers versus the center fibers. USCONEC, a primary MPO supplier, and others offer a higher precision ferrule and alignment version called MTP Elite versus their MTP standard ferrule and connector housing, but at a higher cost/price level.

Optical loss budgets and the number of connections between active equipment types affect and determine the choice of premium or standard MPO connectors. Telecom infrastructure connectivity systems usually have many more passive optical connections versus newer cloud datacenters that have mostly short intra-rack and intra-row between just two devices. Cloud datacenter racks and row of racks have higher density packaging systems that leave much less space for connector plugs versus telecom wiring cabinets and racks. So there are mini-MPO and micro-MPO connector housings to compete against the smaller MXC housing. At this year’s OFC conference and exhibition, Senko and other suppliers had introduced new smaller MPO products. Combined with more flexible strain-reliefs and newer bend insensitive fiber types for both SMF and MMF these new cable assemblies support more confined routing channels.

Industrial automation systems and datacenters also have benefitted from newer designs using circular and rectangular plastic over-shells. Mining and military use MPOs embedded inside circular metal shells.

There are many newer fiber types like 10G performance MMF OM4 that are using color-coded housings like aqua to more easily discern within the rack.

Besides the MXC system, other competing connector and cabling systems now include using a single multi-core fiber with the LC connector. There are up to 12 or more cores within some newer fiber types. Also competing is the Valdor circular 7 fiber ferrule that fits within the SC or LC connector housing and newer E-Shield 19 and 37 fiber circular ferrules that fit within a SC or LC housing. The circular multi-fiber bundle geometry and multi-core fiber solutions help to provide better insertion loss versus the linear single row 16 fiber MPO system.

MPO connectors will still thrive in many market segments while newer multi-fiber connector will also expand their usages and product features and application options.