FreeSpaceOptics

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Free space optics
Opensource Free space optics(FSO) from Ronja is the most cost effective device for the creation of a hotspot between multiple houses instead of MeshNetworking. The Ronja has range of 1.4km and throughput of 10megs. The latency is as the same as with fiber switches, nearly unlimited repeater nodes can be created. This specifically can't be done with MeshNetworking. Lets presume there are 400 houses in a CommunityBlockNetwork. Create as many FSO hotspots as possible. The more hotspots the less DsLam and MeshNetworking nodes will have to be installed reducing the cost of the network considerably. Link these hotspots with a TelephoneNetworkRollout in such a way that the cabling run is minimized which in most cases would mean the cabling connects the CentralOffices orthogonally across the roads. ElectrConsultant can be used to extend the design and improve it with FpGa logic for a max of 100megs with a LED.

Designate one home as the hotspot and lets presume ten surrounding houses have a short range 1km LOS to this hotspot. Install ten FSO links at multiple points on the roof. Connect these FSO links which each have an Ethernet port to a switch and the switch to a router. The router interfaces with either a VDSL2 modem, mesh board or other Ethernet upload node. This will reduce spectrum usage and the need for expensive VDSL, Wi-fi modems and cabling across property boundaries. Note the scalability of a line-of-sight transmitter. To set up a mesh, one can install multiple tubes at one site - http://ronja.twibright.com/mesh.php - while avoiding the interference that would occur with most WiFi antennae. A magnification lens on the receiver and parabolic reflector on the Tx side will increase the range and reduce power consumption. This topology would specifically not be implemented by Neotel and Telkom because they would loose control over the network. South Africa is wasting billions or rands in the laying of fiber lengthwise with the roads so that the Telco's can maintain control. Create a huge network by cabling 50 homes in a street with DsLam. Install 10Ronja's on each house for a total of 500 nodes that with just three repeater Ronja's will have a radius of 3.6km. If these 50-homes hot-spots in turn are connected with 1Gig FSO links we could cover the entire Gauteng area in a matter of months providing everybody with UnlimitedBandwidth. Lasers can't be used due to atmospheric effects that doesn't have the same implication for LEDs.

100 meg is possible with LED
Lasers can't be used because of atmospheric effects. The switching frequency of leds have increased to the point where 100meg is possible.

Reverse engineer commercial 1Gps FSO
Reverse engineer -BoMarc the commercial units such as Terabeam(OpticPatents) and release the designs somewhere on the internet. It will cost around $3000 to reverse engineer the PCB using in http://www.armisteadtechnologies.com/reverse-engineering.shtml. The patents which might cover the design isn't a problem, use a FrontingCompany since we are not in it for commercial gain. The software involves Reed-Solomon for which ElectrConsultant are available. Be careful though when working with a consulting engineer, many of them are great fans of opensource Linux just as long as their hardware and DSP knowledge doesn't get opensourced. Some will request that a NDA be signed and prefer to work with a company who wants to commercialize a product. We in South-Africa are not trying to commercialize it but save this country from an abyss of crime via NetworkCentricWarfare. To study the transimpedence pre and post amplifiers of a normal fiber based switch reverse engineer it. * AmazonForum Books on optical networking * RonjaChips - chips used in Ronja * OpticEthernetBridge * OpticalManufacturers The larger the focusing lens the longer the range * ElectrConsultant - Consultants on FSO designs * OpticPatents - patents on FSO * PaTents * FsoPublication * IrDa

Factors influencing FSO
http://www.seas.harvard.edu/hbbcl/fsoc.html ,,,   http://www.free-space-optics.org/fso_technology.php

Fog: Fog is vapor composed of water droplets, which are only a few hundred microns in diameter but can modify light characteristics or completely hinder the passage of light through a combination of absorption, scattering, and reflection. This can lead to a decrease in the power density of the transmitted beam, decreasing the effective distance of a free space optical link. Fog substantially attenuates visible radiation, and it has a similar affect on the near-infrared wavelengths that are employed in laser communications. Similar to the case of rain attenuation with RF wireless, fog attenuation is not a “show-stopper” for optical wireless, because the optical link can be engineered such that, for a large fraction of the time, an acceptable power will be received even in the presence of heavy fog. Laser communication systems can be enhanced to yield even greater availabilities by combining them with RF systems.

Scintillation: Scintillation is the temporaland spatial variation in light intensity caused by atmospheric turbulence. Such turbulence is caused by wind and temperature gradients that create pockets of air with rapidly varying densities and, therefore, fast-changing indices of optical reflection. These air pockets act like lenses with time-varying properties and can lead to sharp increases in the bit-error-rates of free space optical communication systems, particularly in the presence of direct sunlight. Performance of many laser communications systems is adversely affected by scintillation on bright sunny days. Through a large aperture receiver, widely spaced transmitters, finely tuned receive filtering, and automatic gain control, downtime due to scintillation can be avoided. Use ReedSolomon encoding to minimize the error rate.

Beam Wander: Beam wander arises when turbulent wind current (eddies) larger than the diameter of the transmitted optical beam cause a slow, but significant, displacement of the transmitted beam. Beam wander may also be the result of seismic activity that causes a relative displacement between the position of the transmitting laser and the receiving photodetector Terrestrial Laser Communications Challenges

Physical Obstructions: Laser communications systems that employ multiple, spatially diverse transmitters and large receive optics will eliminate interference concerns from objects such as birds.

Pointing Stability:Pointing stability in commercial laser communications systems is achieved by one of two methods. The simpler, less costly method is to widen the beam divergence so that if either end of the link moves the receiver will still be within the beam. See http://thorlabs.com/navigation.cfm?Guide_ID=10 The second method is to employ a beam tracking system - FsoPatents. While more costly, such systems allow for a tighter beam to be transmitted allowing for higher security and longer distance transmissions.

Increase receiver size to eliminate scintillation effect
OpticalManufacturers makes any size Loupes (loop) lens, the larger the lens the less accurate has to be the aiming. Even a 400mm lens can be manually built.

Fiber like repeater functionality
The Ronja implements IEEE 802.3 Ethernet and  like a fiber node switch allows nearly unlimited repeater links of Ronja's back-to-back before latency becomes an issue depending on the switch type either cut through or store forward -  FsoRepeater

Meshing with FSO
http://ronja.twibright.com/mesh.php Meshing up homes, offices, and buildings: Multiple installations in an area form a mesh. The mesh can exploit multiple redundancies in paths, which can be managed by OSPF and/or BGP protocols. Ownership of the network may be distributed among the participant and still reliable operation can be ensured by employing these protocols.

Meshing with mixed technologies :Ronja can be easily mixed with other network technologies without constraints. Therefore meshes mixing Ronja with ISM band radio wireless devices is for example possible, either as a solution for transition from radio-based mesh to an optical mesh, or as a newly developed solution.

Costs
Outsource the construction to a person paid around R4000/month to hand solder multiple units.

Oreillynet
http://www.oreillynet.com/etel/blog/2007/02/ronja_at_10_mbps_the_next_stag.html "...The promise of Ronja is mesh technology that can deliver 10 Mbps and can be built by an amateur in his or her own home for $100 per unit. The specs are all open-source. Where costs or regulations delay the stringing of cable or fiber, this technology could quickly bring neighborhoods into the twenty-first century in terms of bandwidth and universal service. Applications such as interactive video teleconferencing and remote application access with large remote data storage become immediate possibilities. The Ronja team currently counts 146 registered installations in at least 9 countries. The largest installation is in Prague, where the http://czfree.net/home/index.php community network has 29 links built with Ronja transmitters - http://ronja.twibright.com/czfree.php. A glance at the credits and mailing list archives - http://lists.pointless.net/pipermail/ronja/ reveals a passionate community of amateurs sharing insights and images concerning what parts to order and how to solder, clamp, and install Ronjas. The team is hoping in the near future to extend the range to 3 km and the speed to 100 Mbps. Eventually, with a laser costing $2, they hope to reach 1 Gbps......"

Beam alignment
http://sections.menzonet.org/metropolis/guides/ The picture shows what the transmitter beam looks like from 260m distance (130mm diameter transmitter lens) and the big image is the 90mm transmitter in operation from close, out-of-axis view. Now wait until dark (or at least twilight) and aim the transmitter onto some distant house. Loosen the focus (with #7 wrench) and focus until you see a bright spot. Then tighten. Move the transmitter onto the retroreflector and play with both M8 bolts (two #13 wrenches) and the focus until you get maximum brightness on the retroreflector. Then carefully tighten and watch the spot to be sure you have not drifted during tightening. Measure the received signal strength shortly before you leave the roof and write it down and put it into a safe place for future reference to be able to say if something went wrong.

Ask the other party to aim their transmitter. Then connect the DC voltmeter on 200mV range to the measuring port of the receiver. Then put the focus of the receiver into middle position and fuss around with the receiver until you see some numbers on the meter. Now play with the focus and aiming until you get maximum count. Now freeze down the setting by tightening the nuts down, again watch the meter not to decrease the count (which would mean corrupting the optimum aiming).

Lasers and eye safety
Use 1550nm for eye safe laser transmission or a pulse controlled Ronja system on 880nm. The Tx sends out brief eye safe pulses and waits for a response. Any blocking of the laser will result in Tx sending out only brief pulses until the other Tx indicates no obstruction in the path.

Laser instead of LED
http://www.pointless.net/pipermail/ronja/2003-August/000709.html At 04:24 PM 8/7/2003 +0000, Patrick Deelman wrote:

>So my question is whether someone is still working on a 100mbit version. I >sure would be intrested in that :)

 Me too! 

>Ow and by the way. Why is that radio amateurs are reaching distances from >100 miles (160km) and more (okay i know they

Well, there are a couple of things working against Ronja...

The lower the wavelength, the further the signal will go. Light is a really, really, really high wavelength. (terahertz)

The corollary is that the higher the wavelength, the more information carrying capacity you have. Which means that at lower wavelengths you need wide swaths of spectrum to get a decent amount of information across. High wavelengths such as light can transmit a staggering amount of information in a very narrow frequency range. Ronja is woefully under using the information carrying capacity of light. (think fiber optics)

Finally, radio frequencies are regulated. Light currently isn't. So, to answer your question.. yes, radio amateurs do go 100s of kms and more. They use up huge chunks of frequencies to do so and ultimately their fastest speeds are only a match for the crudest optical setups. More refined optical links will far outpace them. Now, to address distance in Ronja. First and foremost the enemy of distance is aiming this sucker. As you extend the distance, even minute changes on the transmitter end translate into wide arcs at the receiving end. Please realize no mount is 100% solid - even the most solid building sways slightly in the wind, mounts change with temperature, and more. What you need to counteract this all is a precise aiming system. Complex and costly.

Ronja could switch to lasers, it adds cost but gets more photons over the distance. The question with lasers is eye safety - as you crank the power you can cause real damage to people who inadvertently look in the laser's direction - or worse yet point a pair of binoculars in the laser's direction. Every laser beam spreads over distance as a result of focusing and scattering, and that circle can be many meters wide at the receiving end - so it is possible that someone with a window near the receiver could be hurt. To address someone sticking their face in the transmitter lens, there are systems that quickly shut off the laser if contact is lost and does only very quick and eye safe pulses to regain contact, but that once again adds costs. Ronja's current LEDs are safer - they're so bright you turn away and because they're not coherent laser light they won't seriously hurt your eyes for that brief exposure. But that lack of coherency makes them less likely to cross the distance - the non-coherent light, no matter how well it is focused, won't stay together as well as a laser. It's also difficult to find high powered LEDs that switch fast enough to sustain 100Mb.

Finally, there's the curve of the planet. Light goes in a straight line. Lower frequency radio waves can curve around the horizon. This means for a significant distance, you need to get both transmit and receive way high up on a tower to see over the horizon. Microwaves (GHz radio waves) have the same limitations. So, in summary, add precise and constantly adjustable aiming to Ronja, (and the logic to control that aiming) crank up the brightness, maybe add a  encoding method that is handles noise better, maybe use lasers, and you  should be able to get significant distances. Of course, all this makes Ronja harder and more expensive to build.

For me, the perfect Ronja is 100Mb, self-aiming over shorter distances (0.5km to 2km), eye safe, is a circuit that works on a board, and has a auto negotiating twisted pair port. (ie. something that only needs course aiming and doesn't require going out and constantly re-aiming it) With that my friends and I can set up a reliable, high speed, mesh to share bandwidth.

ps. The perfect, perfect Ronja is one that has both the Ethernet TX/RX, Optical TX/RX, and a couple of auxiliary lines into fed into a FPGA. This would give us a programmable Ronja - people could program the FPGA to do whatever they'd like (different link encoding, encryption, autoneg, speed negotiation on the optical link, steering logic, whatever) using a single hardware design. Don't know if that's feasible - I'm a software/logic guy, not a hardware guy. If the hardware is standard, it would be feasible to maybe even construct and sell a kit as a business...

Spectrum scarcity
Instead of each home polluting the spectrum with a WiMax CPE, ten houses forms a hotspot via FSO and only one CPE is shared between them. Vodacom and the NaspersProblem are lying about spectrum availability. There is more than enough spectrum if FSO hotspots are created first. FSO transmitting 1Gps over 2km reduces the need for fiber. Vodacom's specific problem is that they can't request residences to willing house their FSO transmitters and then expect that house to be defrauded by Vodacom to the tune of R5/min for a phone call. We should specifically sell commercial internet via such FSO links which would drive the 2.4ghz and 5.8ghz spectrum polluting Wisps out of business. With 2.4ghz and 5.8ghz spectrum freed up WiMax and MeshNetworking should be used exclusively to connect FSO networks at distances exceeding 4km. We would be able to cover Pretoria and Gauteng in a broadband network in a matter of months.

opensource led drivers
* http://en.wikipedia.org/wiki/RONJA * http://ronja.twibright.com/transmitter/building_pcb.php * http://en.wikipedia.org/?title=Free_machine

Theory behind FSO
* http://www.kultt.co.za/awiki/mediawiki/line_coding.html Line coding * Manchester encoding used in 802.3 Ethernet

Links
* http://www.sctimes.com/article/20090116/NEWS01/101160018&referrer=FRONTPAGECAROUSEL

* http://en.wikipedia.org/wiki/Free_Space_Optics * http://www.free-space-optics.org/fso_comparisons.php 1500nm * http://www.ok2kkw.com/next/qw2008_33km.htm 32km link * http://www.pointless.net/pipermail/ronja/2003-August/000709.html * http://linas.org/mirrors/atrey.karlin.mff.cuni.cz/2002.01.03/~clock/twibright/ronja/electric.html * http://coldstonelabs.org/doku.php?id=ronja * http://www.oreillynet.com/etel/blog/2007/02/ronja_at_10_mbps_the_next_stag.html * http://hackaday.com/2005/06/13/ronja-optical-data-link/ * http://www.alibaba.com/product-gs/209982219/plate_lens.html plate lens

Commercial
* http://www.usaccess-llc.com/mrv.html?gclid=CNfWuZ_4i5gCFQ5NQgodkR-5ew * http://www.usa.canon.com/html/industrial_canobeam/canobeam/index.html * http://www.lightpointe.com/products/fs_g.cfm * http://www.fsoalliance.com * http://www.pavdata.com * http://shop.ebay.com/merchant/fsomn_W0QQ_nkwZQQ_armrsZ1QQ_fromZQQ_mdoZ * http://www.redlinesa.co.za/freespaceoptics.html Commercial system * http://www.americantechsupply.com/mrv_free_space_optics.htm * http://www.terabeam.com/ * http://laseritc.com * http://www.moctkom.ru/indexeng.htm Artolink * http://www.mrv.com/ * Lightpointe