Fibre optic LNBs the future?

[DishDick]

Hi

Satelliteman I did say"Ok so there is little signal loss with fibre and you save a little on amps." but what I was saying is that you are using much more lenghts of fibre than with coax. With coax the max number of parallel cables between multi switches is 4, there is up to 7 with fibre, and its not cheap when bought pre-terminated.

Channel Hopper, all four outputs of the LNB are combined and sent down the fibre. The problem comes when you splt the signal. If you want one cable to run down the estate and you split into two the max signal you get is 50% out of each , so if you feed one fibre to coax converter from the first split it has 50% of signal, 50% goes to next output, but if you split again into 2, 25% of the original signal goes to the fibre to coax converter and 25% towards next converter ie (based on % of original LNB strenght)

100%

1st split 50% to Converter, 50% towards next house (which will have to be split again)

2nd split 25% to Converter, 25% towards next house

3rd Split 12.5% to Converter, 12.5% towards next house

4th split 6.35% to Converter, 6.25% towards next house

5th split 3.125% to Converter, 3.125% towards next house

6th split - signal too low.

Then the way I said

100%

First split 2 way 50% each


One feed left is left unsplit so 50% output, the other is split into 4, 12.5% to each, and each of those split into 4, 3.125% each. One 3.124% output feeds one converter, seven feeds totalling 96.875% go toward house two.

Second house, one feed 3.125% goes to converter six feeds totalling 93.75% go towards house three. you can see even at this point over 70% more signal is going to house three using this method than the single cable (but using six cables not one). These fibre to coax converters do not have a through put and have to fed directly from splitters. Look at the Global/Invacom PDF.

Thats the problem, If the signal converters had a throughput with minimal loss (due to built in amplification, yes we could have one fibre going from house to house.

 

[Channel Hopper]

Thats the problem, If the signal converters had a throughput with minimal loss (due to built in amplification, yes we could have one fibre going from house to house.

Then the most common failure would be that any problem (accidental disconnection for example) in one property would mean a loss for many others.

These fibre to coax converters do not have a through put and have to fed directly from splitters. Look at the Global/Invacom PDF.

The coax would be at the remote end, it is the multiple connections at the head end - either using an active fibre splitter or having an optical LNB with multiple fibre outputs (an octo for example, each output carrying the full signal) - that would be the most convenient device to use in such a system.

 

[DishDick]

Hi Channel Hopper,

"Then the most common failure would be that any problem (accidental disconnection for example) in one property would mean a loss for many others."

I have been involved with two very large systems using this method and ther has never been any problem like this. Due to the distances involved and the duplication caused by the way the fibre system is designed to replace one system with fibre will cost @ one thousand five hundred pounds more than if we could loop through. And the same again extra for the proposed expansion. Three thousand extra pounds worth of fibre optic. Thats on top of 2.5K for the converters ect for existing set up and 2.5 - 3k for proposed larger set up i.e total cost - direct material only 8 thousand 500 pounds. Bugger that - keep coax system!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[Channel Hopper]

You are talking initial costs of replacement though.

If you ripped out the cable, the copper could be sold, reducing the initial outlay.

Unless we are talking at crossed purposes of course.

 

[rolfw]

I guess that there are always going to be exceptions to any rule and it may be that linear developments of houses as you have outlined above require different solutions.

Having said that, the vast number of installations (certainly in the UK) will not be of that type and the fibre solution will save both time and money.

 

[PaulR]

It's horses for courses isn't it?

The good thing is that there is a viable alternative that is better in a few situations. The fact that it doesn't suit every application doesn't means it's no good at all and should be wiped from existance any more than the traditional way has had it and should die away completely!

 

[DishDick]

A few replies -

Channel Hopper, yes we are talking about initial costs 8.5k of them (not incluing any labour or making good costs). Alot of money to anyone. And I don´t think any money got from scrap copper would make much of a dent, if lucky a couple of hundred pounds.

rolfw, it doesnt have to be linear houses. Think of a block of flats, its exactly the same. Lots of extra cable usage (fibre) over a cascading system.

PaulR - Not very impressed with your response. Thought this was a discussion forum. Question posed by thread was "Fibre optic LNBs the Future?" Now I stated my viewpoint and gave examples to explain and justify that view point. I also gave a possible solution to the problems I foresaw. Can you give me a detailed example where in a large building or complex fibre is cheaper or easier to fit?

 

[Topper]

PaulR - Not very impressed with your response. Thought this was a discussion forum.

No you are wrong it is a self help forum for satellite enthusiasts/hobbyists, not a soapbox platform for someone who want to ram their opinions down other people's throats. You need to respect other members and their opinions. As it happens I agree with PaulR's opinion and it is horses for courses. All installations are different and some installations require expensive equipment to ensure they operate efficiently and effectively. Nobody on here has to provide such justifications to you especially members of the moderating staff ;)

As it happens PaulR's post was in defence of fibre equipment stating that it is good there is a viable alternative so why the attitude?

 

[DishDick]

Forum is defined as "a public meeting or assembly for open discussion". And for clarity discussion is defined as " an extended communication (often interactive) dealing with some particular topic ".

Now then I don´t think I have rammed my opinions down other peoples throats as you put it. I thought logically about this system as I was very keen to buy one. But having mapped out the system, I saw what I thought to be a flaw and gave my reasoning. If you look at my first post I asked for any thoughts, incase I had made a mistake or there was a suitable work around. PaulR didn´t appear happy at me knocking a new system but did not give me any kind of counter argument (I use argument in the non-agressive form). It would be nce as part of an adult discussion if people would explain their points of view, moderator or not.

 

[rolfw]

rolfw, it doesnt have to be linear houses. Think of a block of flats, its exactly the same. Lots of extra cable usage (fibre) over a cascading system.

I've thought about a block of flats, as have the designers of the system, I've also costed single and linked blocks of flats, not only can it be less expensive, but also means a smaller dish can be used, or perhaps remove the need for an IF amp.

You appear to be assuming a fibre only system, but in real terms this will at present not be the case and as time passes, splitters and taps will I'm sure be developed to cater for all permutations enabling fibre only systems with great savings in cable and labour.

 

[DishDick]

rolfw. Having been searching on the net today I have found a possible work around. An optical repeater. So I wonder if I fit one of these after split six wheteher this would boast the signal back up to the original level thus allowing six more splts? Hard to find info. Also could there be any negative side effects of this,with current coax amps as we know these amplify noise as well as signal could there be any problems amplifying light?

Also I can´t find any prices for optical repeaters, anyone seen any reasonably priced ones?

 

[rolfw]

You may find it useful to email Global, although they are not the only fibre system manufacturer, I'm sure they will be looking into all scenarios.

 

[Topper]

Well for what it is worth here is my point of view

Things have moved on in recent years a lot has changed in the fibre optic world and your design concept is based upon the premise that an opto coupler/splitter splits at 50% 50% when in reality optocouplers are manufactured in various coupling ratios 50:50 to 1:99, thus the requirement of the first tap would be taken so as to provide sufficient signal to the first drop, whatever ratio that is, determines the maximum number of splits to the end of the line without the need for amplification.

If 10% of the signal is sufficient then a 10:90 splitter is used then with 90% of the signal left you would alter the ratio accordingly for the next feed, but then I am only working from theory and not practice.

 

[DishDick]

Topper, Thanks for that. This is what I mean about this forum I give my view and reasoning and you and others explain to me why it is flawed and/or give a suggestion as to a way around the problem. I am open to other views especially in this case as I am keen to trade up to Fibre, but I want as many advantages as possible.

I have no in depth understanding of these fibre systems. I have read all the info that global have published but they do not have any information on their web site about their splitters. I did email Global with some questions before my first post. When I get a reply from that I will make in depth enquiries about their splitters and see if they are going to make splitters that have different output levels on each side as this would allow me to build a much more cost efficient system, causing the least distruption and least making good and be easier to maintain in the long run.

What I need is a satellite signal distribution via fibre optic guide for dummies!