Increasing Popularity of polarization-maintaining Fiber

Optical networks have become popular due to increasing demands for bandwidth. It becomes important to use existing fiber-optic networks very effectively because installation of new fiber-optic networks is very expensive. Dispersion and attenuation are the main parameters that limit the optical networks. The uses of two polarization axes are improved by the efficiency of optical networks which are very much similar to the technology used in radio technologies. The use of two polarization planes is allowed because of the use of polarization maintaining splitter.

Theoretically, there is no birefringence in an optical fiber with a circular core, and in such an optical fiber the polarization state does not change during propagation. However, in reality, due to external perturbations or manufacturing imperfection in an optical fiber, a small amount of birefringence is always present. Such birefringence is inherently random, and in an optical fiber between two polarization modes, it results in random power coupling. The output polarization state then becomes unpredictable and also differs with time.

PM fibers need to meet critical optical and mechanical specifications, such as attenuation and tensile strength. In characterizing their birefringence properties polarization maintaining isolator have two specifications – beat length and holding (H) parameter. These are complex measurements, but characterizing how well the fibers maintain the two polarization modes they are necessary.

By intentionally inducing uniform birefringence along the entire fiber length a polarization-maintaining Fiber (PM Fiber, PMF) maintains two polarization modes, hence they prohibit random power coupling between two polarization modes.

In a single-mode fiber, the transmission of a source laser’s output is done with two linear polarization modes that propagate at right angles to each other. For a moment imagine that this fiber is an ideal single-mode waveguide:

• the fiber and source laser temperatures always remain constant;
• Polarization maintaining circulator does not have bends and no loss;
• there is perfect uniformity in the core material;
• Compared to the cut off wavelength the laser wavelength is greater, and all the laser energy is concentrated in the core;
• Lateral stress is zero (no external stress from cabling, placement, supports, etc., or even, hypothetically, no gravity or air pressure).

Know about the Working of Fiber optic splitter

Working of fiber optic splitter

Whenever in a network there is the transmission of the light beam it needs to be divided into two or more light beams and for this purpose, a fiber splitter is used.

Whenever there is the transmission of the light signal, the light energy cannot entirely concentrate in the fiber core. Through the cladding of the fiber, a small amount of energy will be spread. The transmitting light in an optical fiber can enter into another optical fiber if two fibers are close enough to each other. Therefore, you can achieve the reallocation technique of optical signals in multiple fibers.

Splitter never generates power nor do they need it. Hence, it is a passive device. Splitters do not even contain any electronic components. It is a simple device. A fiber optic splitter is also referred to as a beam splitter.

In most fiber optic networks splitters are widely used. It consists of numerous input and output terminals, which are majorly applicable to a passive optical network like GPON, BPON, FTTX, EPON, FTTH, etc.

Into two types there is a division of the fiber optic splitters: Fused Biconical Taper (FBT) splitter and PLC splitter.

The most commonly used splitters are the FBT splitters. FBT splitters are accepted everywhere and are mainly used in passive networks.

PLC Splitter

PLC refers to a planar lightwave circuit. PLC splitter makes use of an optical chip as a micro-optical device so that the input signal can be split into various outputs. At the edge of the chip, there is the presence of a light circuit in ribbon form that is mounted on a carrier and fibers. PLC splitter divides the incident light beam (input light signal) into two or more light beams (output light signal) with the use of a fiber splitter chip. As the material of the lightwave circuit PLC splitter adopts silica glass. In PLC splitter the substrate, waveguide, and lid are three basic layers. PLC splitters can be further categorized into different types for various applications which include LGX box PLC splitters, block less PLC splitters, ABS PLC splitters, tray-type PLC splitters bare PLC splitters, mini plug-in type PLC splitters, and 1U rackmount PLC splitters.

Simulating Multi-Fiber and MPO Cable Links

Multi-fiber cabling is used both inside data centers and across vast field networks in today’s advanced fiber-optic networks because deploying large counts of fibers using as little physical space as possible provides the most efficient approach. On a basic level, MTP breakout cable consists of a ribbon cable that is then surrounded by a protective outer jacketing. When it comes to fiber counts this ribbon and/or multi-fiber cables are available with several options.

In a data center between racks, one can have 12 or 24 fiber patch-style cables that connect devices. 

Across the network between sites, a larger field cable in the ground will have several of these resulting in larger fibers counts like 72, 144, 288, and so on. At the ends of some links, fibers may be individually terminated but those between the gear inside the data center often make use of MPO style connectors to reduce the number of total connections.

NEED TO SIMULATE MULTI-FIBER MPO LINKS

There are some primary applications where there is a simulation of multi-fiber links in the lab environment:

Device certification – is provided by the manufacturer or those deploying the equipment

Latency/delay validation – replicates expected network

Simulating real-world conditions is a critical part of the quality assurance process particularly for transceiver and device manufacturers who are designing or certifying their technology. In case an engineering team is designing a new 100G transceiver with a 500m distance specification and MPO connectivity then it needs to be tested over a real 500m MPO breakout cable to make sure that before going into production it is optically functioning as expected over that distance. The QA team may run a final test over the simulated link once a finished product is in production just to make sure that before shipping to the customer the product passes its final inspection.

Secondly, while validating or certifying the necessary equipment before purchase, engineers at service providers and data centers tasked with selecting and deploying MPO breakout cable in their network may wish to replicate their unique fiber links. Spending a large sum of money on equipment is the last thing any network engineering team wants to do and later gets to know that it doesn’t meet all of the needs.