Dear all, We're an FSO vendor - as well as our other radio and micrwoave products. Actually I feel we should pitch in on the LEDs vs lasers - a topic we know very well: - LEDs are limited in power and bandwidth (more than 50Mbps at reasonable power is a real problem for the raw LED devices) - LEDs fade with lifetime, and there is no closed-loop control to compensate this - LEDs don't collimate into very nice beams - LEDs generally are at 975nm which is the same as some laser products (such as our 980nm Access series) 980nm transmits better at long distances than shorter wavelengths, but at short distances there is no disadvantage with short wavelengths - LEDs are cheaper devices than laser, which is actually the only reason they are used. There is no advantage of LEDs with dust, except in the case of a few vendors that have narrow-aperture laser systems (avoid those: known to cause problems). We have LED technology and only use it for very short (a few feet) customised and indoor links. For outdoor links, use laser, it's far better.
Using Laser we have achieved "better than 5 nines" for some operators even in foggy areas like London, on sub-kilometer links. For one network operator (broadband ISP) they have under 15 seconds downtime over 7 years - 155Mbps sub-kilometer links - which rather proves the point. Though we have long distance laser installations at 4km+, those require relatively clear conditions, or RF resilient path. Generally, below 1km (say, 3/4 a mile) laser is absolutely a great solution. In the USA, our lasers are deployed with cell carriers like Nextel, for example, for backhaul from base stations on similar short hops. Elsewhere in the world we have several hundred lasers for individual cell carriers where microwave was considered too expensive. Equipment reliability, vendors differ enormously - caveat emptor. We have installations back to 1997 still in service, so we're good on that score. Some features like peltier cooling (solid state TEC) radically improves lifetime, as laser lifetime drops off with temperature. Automatic Transmit Power Control (ATPC) increases TX power in fade conditions, and reduces in clear weather, improving availability and lifetime. Power supplies generally mounted indoors and DC run to the laser units; though it is possible to put PSUs in roof/tower locations. Generally, our customers "fit and forget" and just as you say, walk away and leave them running. Software NMS tells you the links are solid and working. Laser certainly has it's place: you get no inteference and high 100Mbps and true Gigabit Ethernet throughput. For short links, laser is currently cheaper than E-band MMW and (assuming a good product) no less reliable. For the longer links, OFDM radios and licensed microwave (we make/sell them too) are the best options. </sales pitch> Anyone who wants information or some real-world case studies, please don't hesitate to ask - we have many, including WISPs. Questions/comments welcome - Best regards Stephen Patrick CableFree Solutions www.cablefreesolutions.com [mail sent in text format: advance apologies if it arrives in HTML, our ISP/mail server is the culprit when this happens] -----Original Message----- From: George Rogato [mailto:[EMAIL PROTECTED] Sent: 16 March 2007 08:06 To: WISPA General List Subject: Re: [WISPA] PtP pricing Whats the reliability factor? I've been thinking of adding fso for a couple links now for a couple years. Now I could put 100megs duplex to use rather than waste the spectrum. But how well does this stuff stand up? Haven't heard much about anyones experiences good or bad. is it 6 9's? does the power supplies burn out or the units need to be repaired often? Or are they switch em on and walk a way for a few years? George Marlon K. Schafer wrote: > Hard to beat orthogon! > > And for a link that short I'd look REALLY hard at fso gear. > > http://www.plaintree.com/ > > Plaintree has some cool infrared systems. They handle dust and such > better than lasers. > > If you want laser systems, EC has some that are pretty cool too. Not > too expensive either. > marlon > > ----- Original Message ----- From: "George Rogato" > <[EMAIL PROTECTED]> > To: "WISPA General List" <[email protected]> > Sent: Thursday, March 15, 2007 9:13 PM > Subject: Re: [WISPA] PtP pricing > > >> Non set budget. >> >> >> Marlon K. Schafer wrote: >>> what's the budget? >>> >>> ----- Original Message ----- From: "George Rogato" >>> <[EMAIL PROTECTED]> >>> To: "WISPA General List" <[email protected]> >>> Sent: Thursday, March 15, 2007 3:02 PM >>> Subject: [WISPA] PtP pricing >>> >>> >>>> I need a couple very short range PtP links. A few hundred feet at >>>> most for each one. Something that did close to 50 or even 100 megs >>>> duplex would be good >>>> >>>> Has anyone worked with Free Space Optics and can advice? >>>> Also looking to be frugal. But don't want 5 gig. >>>> -- >>>> WISPA Wireless List: [email protected] >>>> >>>> Subscribe/Unsubscribe: >>>> http://lists.wispa.org/mailman/listinfo/wireless >>>> >>>> Archives: http://lists.wispa.org/pipermail/wireless/ >> >> -- >> George Rogato >> >> Welcome to WISPA >> >> www.wispa.org >> >> http://signup.wispa.org/ >> -- >> WISPA Wireless List: [email protected] >> >> Subscribe/Unsubscribe: >> http://lists.wispa.org/mailman/listinfo/wireless >> >> Archives: http://lists.wispa.org/pipermail/wireless/ > -- George Rogato Welcome to WISPA www.wispa.org http://signup.wispa.org/ -- WISPA Wireless List: [email protected] Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/ -- This email has been verified as Virus free Virus Protection and more available at http://www.plus.net -- No virus found in this incoming message. Checked by AVG Free Edition. 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