Advantages and Disadvantages of Fibre Optics


Introduction


Optical Fibre is now used extensively throughout the communications industry in both Telecommunications and Data Communications. It extends from long haul transatlantic ocean cables to short in-building links. It has many advantages over traditional copper cables. The fibre industry continues to enjoy significant growth year on year as our demand for speed and capacity grows. It is no longer about Fibre connecting POPs (Points of Presence) on a backbone up and down a country. We now expect a fibre connection to every home, house, flat, apartment business etc. The demand we see in the Fibre industry is a global phenomenon.

Optical Fibre has significant advantages over a copper solution, and it would be impossible to cover all of these in this document. However, we will draw a comparison to some of the significant advantages and some of the disadvantages.


Fibre - What Is Optical Fibre?


Electrical information/data is converted to light pulses via a transceiver, then transmitted down the Fibre Optic strand. This light pulse will propagate along the length of the Fibre. The light will be received by a transceiver, where it will be converted from light pulse/s back to electronic data. The speed and bandwidth carrying capacity of a Fibre Optic link/s is significantly higher than that of a copper-based system. The fibre core can be cabled up and deployed in Military, Commercial, Government, Industry and the home. The Fibre can be cabled up to meet the exacting specification or application, Internal, External, Armoured, Harsh environment, Under-ground or Under Sea. We currently have an ever-increasing lattice of fibre Optic Cables around our globe, delivering services Video, Voice and data transmissions. 

Common Fibre Optic Types

 

This can best be defined as three Fibre types. The table below better describes constructions and types. For this exercise, we will only concentrate on the SMF & MMF Fibres. We will deal with POF (Plastic Optical Fibres) separately.

SMF - Single-Mode Fibre Optic


Single "Mode" refers to the path the light travels and propagates along the Fibre. The core of a Single -Mode fibre is Ø8-9um. In a single-mode fibre, there is only one single path for light to propagate. There is no dispersion with SMF. With a small core Ø9um, the difference between refractive indices of the core and cladding is minimal, which helps lower attenuation. The cost of single-mode Fibre is less than MMF. However, generally speaking, the active equipment on single-mode networks are laser-based and more expensive than those on LED base MMF networks. Diag 2 illustrates fundamental differences between SMF & MMF.

MMF - Multimode Fibre Optic 


Multi-Mode is a large core fibre when compared to a single-mode fibre. Multimode  typically has a Ø50 or 62.5um core. (Please see Diag 2 above) Given the core's size, multiple and simultaneous paths of light can propagate the core. The difference between the refractive indices and the core is large, giving rise to signal distortion, dispersion and increased attenuation. It is generally used in data comms applications, short distances audio, video, CCTV, Lan based applications. Multi-mode Fibre is available either as a Step-Index or Graded index. Latterly it is the Graded index OM2-OM5 where we are seeing the growth.


Optical Fibre and its Advantages


As mentioned earlier in the document, the globe has a latticework of Fibre networks connecting our world. Yes, other forms of communication, such as Satellite, Micro Wave, WiFi and Copper but all of these come back to Fibre, either the backbone, backhaul or transatlantic connections. Fibre is without question, the most efficient means of providing connectivity. Let's have a look at some of the advantages as compared with copper.


Performance             


Faster Speeds greater bandwidth. Enable Commercial, Industrial residential to enjoy. Fast communication with file transfers / Video on Demand VOD / Mobile connectivity / 8k TV etc. This is probably the single biggest asset of a Fibre based network.


Easy to install   
     

Cables have been designed to meet particular applications, could be Duct / ADSS / Aerial / Sea / Armoured / Non-metallic etc. Provided the installation criteria is met then the Cable will perform to specification. Great time care and research has taken place to give the cable designers the tools they need to ensure the preservation of the Fibre, for the desired application.


Cable Construction         


Smaller diameter, smaller bend radius, lighter better return onavailable space.


Bend insensitive Fibre     


Giving greater flexibility from a design perspective, more tolerant from an installation perspective.


Capacity


Comparing a strand of copper v strand of Fibre, well there is no comparison the Fibre has significant capacity above that of copper of similar diameter. Therefore for a given diameter of Cable, there would be significantly more capacity to service the demands. 


Susceptibility     


Light signals in fibre cables are not susceptibility to EMC / No cross talk reduced interference better performance. 


Security            


Not possible to tap and decode EMC signals as there are none.


Cost-effective    


Fibre cable is significantly more cost-effective than a copper cable, given the capacity and performance. From a material perspective Fibre is cheaper than copper. 


Distance             


Fibre can achieve greater distance than copper. Loss of signal in fibre is less than that in copper.


Good life cycle


Typically 50-75yrs dependent on application.


Optical Fibre and its Disadvantages 


Training             


Having a trained workforce with knowledge and skills to work with fibre.


Termination             


Difficult to splice needs specialist equipment and training.


Installation             


Can be more expensive to install, care to be taken during this process. If you bend the Cable beyond its limit, it may break.


Fibre Selection 


If the project is a move or a change or extension to an existing network, then the fibre type should be relatively straight forward. Review existing Fibre consider applications speed and bandwidths, distances involved, possible up-grade with enhanced Fibre which needs to be fully backwards compatible with existing. Perhaps it is a tender/RFQ in which case there will be a full and detailed specification. Ensure that source materials are from approved suppliers re Fibre & other associated materials. When auditing a particular supplier then consider Cable design tools and  operating systems, environmental awareness is essential. Consider ISO9001 / ISO14001 / ISO18001 ROHS & CPR – Construction Products Regulation.


CMW only stock optical cables from responsible, sustainable sources that comply with ISO 9001 / 14001 / 18001. Visit www.cmwltd.co.uk We have Optical Fibre & Cable experts available to deal with your request.


Fibre Selection - Single Mode or Multimode


The client and the network design will  primarily dictate the fibre type. However, it is worth reviewing the design, opportunities to modify or enhance may present themselves. It is good practice to understand the application too better advise on fibre selection.  


Optical Cable Jackets: PVC / LSZH 


This is an area that necessitates the need to have a very detailed understanding of the application and the environment where the Cable will be deployed. For this exercise, we will take a very simplistic view. We can initially create two mutually exclusive zones where cables are deployed, and where the standards applicable are significantly different.

They are quite simply either Internal or External applications. 


External


PVC (Polyvinyl Chloride) is possibly one of the most widely used cable sheaths for external applications. It is Durable, Flexible & with good longevity. This is generally used in ducts over ground or direct burial.


Internal


The standard jacket type for internal optical Cable is LSZH, also known as LSHF / LSOH / LS0H. There are rigorous standards that these cables must conform to (BS-EN 50525-11) When burnt the LSZH cables give off very little smoke and no toxic fumes, particular ref to hydrogen chloride. It is imperative that the application and standards are fully understood before selecting a cable type. 


Optical cable types. Loose Tube or Tight Buffered


Generally speaking, we can look at the cable designs which fall into one of two camps.
This is not an absolute definitive rule, but it is a good guide for cable design v application.


Tight-Buffered 


This is an internal distribution cable 900u buffered fibre 4-24. Typically a data Comms application. Dry construction with some protective layer sometimes rodent protection in the form of glass yarns and an LSZH sheath. It is also possible to make Simplex & Duplex patch cables utilising the 900u buffers with additional strength, generally in the form of Kevlar wrapped around the buffer and an LSZH sheath typically Ø2.5/3.00mm.


Loose Tube 


This is generally associated with external Cable. Typically a Telecoms application, but not exclusively, it can be used on campus / CCTV applications. Construction is either uni-tube or multi-tube. Typically 12 fibre per tube. Fibre count from 4-288 and beyond. All these cable constructions can have metallic or non-metallic armouring. 
We also have new developments with Ribbon fibre and ADSS All-dielectric Self-Supporting aerial cables which are more associated with the Telecoms and loose tube construction.


Micro Modules


A new addition to the cable constructions is the Micro Module. This is a variant of the loose tube, and it has smaller diameter approx. 1.6mm it forms a flexible and easy to access package. Multiples of these are laid up to make high fibre count cables. This construction reduces the diameter and the weight of the Cable. 


External v Internal 


Largely dependent on application.

External cables are of rugged construction to protect the Fibre in harsh environments, moisture, changing temperatures. There have been significant advancements in materials, dry constructions which have made working with loose tube easier. These cables are generally associated with long haul telecom applications.
Internal cables are tightly regulated concerning sheath material and burning characteristics LSZH sheath as discussed earlier. These cables are of a lighter construction, generally easy to work with from and installation and termination perspective. 


Fibre Count


Loose tube: cable constructions vary vastly. Its structure generally has a tube or a module, multiples of these are laid up to make a cable core. This core could be anything from 12 -864 fibres and beyond.

Tight buffer: cable construction is more focused around the 900u subunits 2-24 Fibre generally, but this can also be 96 or 144. 


Conclusion


Our demands for information continue to grow globally, with increased demand from the commercial, industrial and residential sectors. We demand quicker, faster better, to run applications such as - VOD, Video Conferencing, 8K TV, Gaming, Gambling and the increased demand to work from home. Network Operators continue to invest heavily in infrastructure to meet the ever-increasing demand. This infrastructure is based around FIBRE.

Fibre is invariably used within all present-day and future networks. There is no commercial substitute for Fibre currently. The difference between a copper and fibre network is so significant. It is not possible or feasible to make a like for like commercial comparison – Fibre is the only way to go. 

You can find out about the range of fibre products available from CMW by clicking here. You can also speak to the team by emailing sales@cmwltd.co.uk