[Ronja] Ronja Digest, Vol 58, Issue 13
eldis
eldis111 at seznam.cz
Fri Feb 22 14:03:39 GMT 2008
ML6652 might look like good choice, but I wouldn't recommend it.
There have been reports of malfunctions and bugs in this chip. In my
opinion this is because of very noisy enviroment.
As you know, fiber optics (ML6652 standart usage) means,
that manufacturer is not taking into consideration that much noise on
RX. When some bad packets arrive,
ML6652 can freeze (and will, on ocasions).
I've worked on 100Mbps FSO some time ago, even had chance to speak with
designer of 10Ghz radio.
He told me about problems with interpreting damaged data, and flows in
cheap convertors.
My design use for TX - MAX3263,
RX - MAX3657 for TIA, and MAX3645 as limiter.
Convertor based on RTL8305SB, IMHO there are better choices, but only in
+1000 quanties
Cheap PIN photodiode from Vishay (1,8pF).
This design worked, but never finished.
As for VCSEL, it is good choice, if you find some with enought power.
Than you don't need that MAX3263, basic regulation is sufficient.
BTW, things that have pins visible are easy to solder even on home-made
board with basic soldering tools,
BGA's are harder :)
eldis
> I am working on a 100 mbps design based on ML6652 and LED driver is
> MAX3263 and Reciver uses philips SA5211 as transimpedance Amplifier
> .Will be releasing first shematics in a day or two . I am planning to
> use VCSEL laser to begin with .
>
> Since ML6652 has autonegotiation feature all those will be no problem
> for 100mbps design . Only problem will be soldering ML6652 which will
> need specail facility and might not be possible in a home lab .
>
> PK Yaduvanshi
>
>
> On 22/02/2008, *ronja-request na lists.pointless.net
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> Today's Topics:
>
> 1. Re: What is holding back 100 mbps (J.D. Bakker)
> 2. Re: What is holding back 100 mbps (J.D. Bakker)
> 3. Re: What is holding back 100 mbps (Pavel Krejci)
> 4. Re: What is holding back 100 mbps (Thomas Egenhofer)
> 5. Re: What is holding back 100 mbps (Gregory Maxwell)
> 6. Re: What is holding back 100 mbps (J.D. Bakker)
> 7. Re: What is holding back 100 mbps (Daniel Strnad)
> 8. Re: What is holding back 100 mbps (Gregory Maxwell)
> 9. Re: What is holding back 100 mbps (alex dinovitser)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 21 Feb 2008 13:11:00 +0100
> From: "J.D. Bakker" <jdb na lartmaker.nl <mailto:jdb na lartmaker.nl>>
> Subject: Re: [Ronja] What is holding back 100 mbps
> To: Twibright Ronja <ronja na lists.pointless.net
> <mailto:ronja na lists.pointless.net>>
> Message-ID: <p0624052ec3e31a35c4dd@[130.161.115.44
> <http://130.161.115.44>]>
> Content-Type: text/plain; charset="us-ascii" ; format="flowed"
>
> >---- Deepak Mishra <xask.linus na gmail.com
> <mailto:xask.linus na gmail.com>> schrieb:
> >> Hi people,
> >> 100 Mbps open source FSO, I think would revolutionize the
> wireless link
> >> scene.
> >> I am really confused as to what is really holding back the
> development of
> >> 100 Mbps RONJA, even when every thing is open source and free.
> >
> >The fact that I have to go to work? Anyone has resources to pay one
> >developer fulltime?
>
> What Clock said.
>
> I have a prototype PCB for a 100MHz RX/TX unit but simply have had no
> time to test/tweak/enhance it. LED fall time is the issue so far; I
> know what to do about it, but (payed) work takes precedence over a
> GPLed project.
>
> JDB
> [already have a kit/prebuilt boards deal set up with my commercial
> partners in Taiwan]
> --
> LART. 250 MIPS under one Watt. Free hardware design files.
> http://www.lartmaker.nl/
>
>
>
> ------------------------------
>
> Message: 2
> Date: Thu, 21 Feb 2008 13:19:11 +0100
> From: "J.D. Bakker" <jdb na lartmaker.nl <mailto:jdb na lartmaker.nl>>
> Subject: Re: [Ronja] What is holding back 100 mbps
> To: Twibright Ronja <ronja na lists.pointless.net
> <mailto:ronja na lists.pointless.net>>
> Message-ID: <p06240530c3e31c4d42ac@[130.161.115.44
> <http://130.161.115.44>]>
> Content-Type: text/plain; charset="us-ascii" ; format="flowed"
>
> > > > I start this thread to exactly pin point the problems of a 100
> >Mbps RONJA.
> >> > Let us reach to a conclusion as to what exactly must be
> modified.
> >> >
> >> > Let us start with the LED,
> >> > 1. To transmit at 100 mbps,we must find an LED which can
> switch on and off
> >> > in 1 ns.
> >that's not neccessariliy true. if you wanna use 2-level encoded
> >signals like now ,you'd run into several problems.
> >first is you would have to change the encoding of the MLT3 signal to
> >2-level signal which is suited for optical transmission. in easiest
> >case manchester code.
> >which would result in a 0.5ns signal-time.
>
> Why does a 100Mbit Manchester encoded signal (with 10ns per bit) have
> a 0.5ns signal-time? Methinks you are off by an order of magnitude.
>
> JDB
> [not that you'd want to use Manchester if you can help it...]
> --
> LART. 250 MIPS under one Watt. Free hardware design files.
> http://www.lartmaker.nl/
>
>
>
> ------------------------------
>
> Message: 3
> Date: Thu, 21 Feb 2008 19:06:14 +0100
> From: Pavel Krejci <krepa na seznam.cz <mailto:krepa na seznam.cz>>
> Subject: Re: [Ronja] What is holding back 100 mbps
> To: Twibright Ronja <ronja na lists.pointless.net
> <mailto:ronja na lists.pointless.net>>
> Message-ID: <47BDBD96.7030505 na seznam.cz
> <mailto:47BDBD96.7030505 na seznam.cz>>
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> ------------------------------
>
> Message: 4
> Date: Thu, 21 Feb 2008 21:59:35 +0100
> From: Thomas Egenhofer <antitron na web.de <mailto:antitron na web.de>>
> Subject: Re: [Ronja] What is holding back 100 mbps
> To: ronja na lists.pointless.net <mailto:ronja na lists.pointless.net>
> Message-ID: <1203627575.4502.8.camel na localhost.localdomain
> <mailto:1203627575.4502.8.camel na localhost.localdomain>>
> Content-Type: text/plain
>
>
> > Hi all,
> > The discussion so far
> >
> > Saad Shakeel says
> > 2. Need equally fast photodiode and 74xx ics
> > 3. faster ne592 alternate as it only works at 10nS
> > 4. we might be able to use the bf908 since it supports upto
> 1 GHz.
> >
> > Thomas Egenhofer says
> > - Think over encoding technique
> > 1. 2 level encoding at 100 mbps could run into problems.
> > 2. 2 level encoding would require rise and fall times of .5ns !
> sorry.. looks like a zero shifted around in my brain. should be 5ns i
> think..
>
>
> > 3. MLT3, coming from the LAN card could be used (30ns),
> requiring in
> > rise and fall times of 15ns of LED
> > 4. It would require redesigning the transmitter
> i dont belive you can skipp this if used with 2level encoding^^ also
> keep in mind that signal-times of 10ns are quite tricky to handle.
> even
> fast logic can easily produce a delay of up to 15ns which can
> cause many
> problems with signal-timing in general.
>
> > 5. He already has a prototype MTL3 reciever at
> > http://home.arcor.de/positiveelectron/files/MLT-3-receiver.png
> >
> > Meanwhile CD930 shows us he already has a 100 Mbps version, but
> alas the in
> > the clutches of proprietary license
> > He has videos at
> > http://www.youtube.com/watch?v=9h3hDm32kv4
> > http://www.youtube.com/watch?v=YcjaJhMHcNk
> >
> > and even better people like Jim Thompson are waiting to be
> convinced to
> > finance a 100 Mbps version.
> >
> >
> > What are we waiting for ?
>
>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Thu, 21 Feb 2008 16:06:35 -0500
> From: "Gregory Maxwell" <gmaxwell na gmail.com
> <mailto:gmaxwell na gmail.com>>
> Subject: Re: [Ronja] What is holding back 100 mbps
> To: "Twibright Ronja" <ronja na lists.pointless.net
> <mailto:ronja na lists.pointless.net>>
> Message-ID:
>
> <e692861c0802211306q5764399fuc5bd1e92bb70c18b na mail.gmail.com
> <mailto:e692861c0802211306q5764399fuc5bd1e92bb70c18b na mail.gmail.com>>
> Content-Type: text/plain; charset=UTF-8
>
> On Wed, Feb 20, 2008 at 4:20 PM, Thomas Egenhofer <antitron na web.de
> <mailto:antitron na web.de>> wrote:
> [snip]
> > first is you would have to change the encoding of the MLT3
> signal to 2-level signal which is suited for optical transmission.
> in easiest case manchester code.
>
> This makes no sense to me. Going to a higher encoding level should
> trade bandpass for SNR (and linearity) requirements.
>
> It might not be a huge win given the channel characteristics, but
> saying that it would need several orders of magnitude more bandwidth
> (which is what saying .5ns rise time is saying)
>
> With a proper EQ (which would be easy with an all digital
> modulator/demodulator) higher level encoding should work well across
> the optical channel.
>
>
>
> ------------------------------
>
> Message: 6
> Date: Thu, 21 Feb 2008 22:32:36 +0100
> From: "J.D. Bakker" <jdb na lartmaker.nl <mailto:jdb na lartmaker.nl>>
> Subject: Re: [Ronja] What is holding back 100 mbps
> To: Twibright Ronja <ronja na lists.pointless.net
> <mailto:ronja na lists.pointless.net>>
> Message-ID: <p06240535c3e39dc69b50@[130.161.115.44
> <http://130.161.115.44>]>
> Content-Type: text/plain; charset="us-ascii" ; format="flowed"
>
> >With a proper EQ (which would be easy with an all digital
> >modulator/demodulator)
>
> In dedicated silicon or a larger FPGA, yes. In gates or discrete
> hardware, not so much.
>
> JDB
> [ran into this when designing a 100Mbps synchronizer, which is quite
> a bit easier than an EQ. For ASICs this is a solved problem, but I
> wanted/needed to do it in commercially available gates]
> --
> LART. 250 MIPS under one Watt. Free hardware design files.
> http://www.lartmaker.nl/
>
>
>
> ------------------------------
>
> Message: 7
> Date: Thu, 21 Feb 2008 22:35:39 +0100
> From: "Daniel Strnad" <daniel.strnad na tiscali.cz
> <mailto:daniel.strnad na tiscali.cz>>
> Subject: Re: [Ronja] What is holding back 100 mbps
> To: "Twibright Ronja" <ronja na lists.pointless.net
> <mailto:ronja na lists.pointless.net>>
> Message-ID: <op.t6v8xpt2n6qjls na daman>
> Content-Type: text/plain; format=flowed; delsp=yes; charset=utf-8
>
> Hi all,
> I am not very interrested in topic for some time, but I have few fast,
> suitable for 100Mbps, photodiodes. I planned some design with it,
> but now
> I offer it for experiments to you. It's FCI-HR008
> (http://www.datasheetarchive.com/pdf/1382205.pdf). It has capacitance
> 0.8pF at 5V! Price: 1 000CZK (40?) per piece.
>
> DS
>
>
>
> ------------------------------
>
> Message: 8
> Date: Thu, 21 Feb 2008 16:36:08 -0500
> From: "Gregory Maxwell" <gmaxwell na gmail.com
> <mailto:gmaxwell na gmail.com>>
> Subject: Re: [Ronja] What is holding back 100 mbps
> To: "Twibright Ronja" <ronja na lists.pointless.net
> <mailto:ronja na lists.pointless.net>>
> Message-ID:
>
> <e692861c0802211336n22170588s79deb3def160857f na mail.gmail.com
> <mailto:e692861c0802211336n22170588s79deb3def160857f na mail.gmail.com>>
> Content-Type: text/plain; charset=UTF-8
>
> On Thu, Feb 21, 2008 at 4:32 PM, J.D. Bakker <jdb na lartmaker.nl
> <mailto:jdb na lartmaker.nl>> wrote:
> > >With a proper EQ (which would be easy with an all digital
> > >modulator/demodulator)
> >
> > In dedicated silicon or a larger FPGA, yes. In gates or discrete
> > hardware, not so much.
>
> Yes. mac->fpga->adc/dac->current amp. Solved. But making that
> inexpensive? ... :-/
>
>
>
> ------------------------------
>
> Message: 9
> Date: Thu, 21 Feb 2008 22:59:07 -0800 (PST)
> From: alex dinovitser <adinov na yahoo.com <mailto:adinov na yahoo.com>>
> Subject: Re: [Ronja] What is holding back 100 mbps
> To: Twibright Ronja <ronja na lists.pointless.net
> <mailto:ronja na lists.pointless.net>>
> Message-ID: <293348.55216.qm na web32708.mail.mud.yahoo.com
> <mailto:293348.55216.qm na web32708.mail.mud.yahoo.com>>
> Content-Type: text/plain; charset=iso-8859-1
>
> This is surely analogous to the high speed fiber communications
> such as DWDM.
> The current standard here is 10Gb/s per channel. That corresponds
> to an
> electrical bandwidth of at least 5GHz. These optical devices are
> specified to
> 10GHz.
>
> The diodes required for this application need to have a very low
> capacitance.
> This capacitance (almost) solely determines the speed of the resulting
> transimpedance amplifier.
> A diode's capacitance depends on its area. It also depends on the
> applied
> reverse voltage. However, it would be wrong to use and avalanche
> diode in
> avalanche mode! This diode detects individual photons, and each
> event has a
> 'quench time' (it works very similar in principle to a
> geiger-muller tube)
> which means they will saturate with very low ambient light levels!
>
> Avalanche type diodes can be suitable if operated at lower voltage
> because of
> their small area and a wide pIn channel that results in lower
> capacitance. They
> are very expensive however.
>
> The small area for a suitably fast RONJA diode might requires some
> thought of
> the optical system.
>
> I still think the best detector theoretically would be a
> pyroelectric device.
> No suitable affortable devices so far:-(
>
>
> AD
>
>
> --- Pavel Krejci <krepa na seznam.cz <mailto:krepa na seznam.cz>> wrote:
>
>
> ---------------------------------
> Can you tell us, please, at least which chipset from MAXIM it is?
> Thanks
>
> PK
>
> CD930 napsal(a): Sorry...no, maybe later. But...TX,RXis
> MAXIM chipset,
> mediaconvertor MARVELL 1108 (beforeused Micro-Linear), laser is
> 870nm/10mW and
> photodiode is PDB-C102.
> Tested (tx lens 11cm, rx fresnellens 20cm) on 2500m. RSSI go to AD
> and Atmel
> CPU (LCD and RS232c).
> M.
>
> -----Original Message -----
> From: Deepak Mishra
> To: Twibright Ronja
> Sent:Thursday, February 21, 2008 9:48 AM
> Subject:Re: [Ronja] What is holding back 100 mbps
>
>
> Hi CD930,
> Sure dont release the PCB, but you could give us suggestions
> onimproving the
> RONJA design to 100 Mbps.
> You could point us in the right direction, like the
> modulationtechnique to use,
> coding technique, or LED used ,or lasers, otherpitfalls you
> encountered ?
> Would you like to support a "free" cause ?
>
> Regards,
> Deepak
>
> On 21/02/2008, CD930 <cd930 na centrum.cz
> <mailto:cd930 na centrum.cz>> wrote: HiVladimir.
> Sorry, this development was for one firm from our city.
> I must not publish circuit PCB :(
> But....some ideas i am here publish along the years.
>
> In future looking on 1Gpbs..... avalanche photodiode with 200V dc :)))
> roung again toy gadget.
>
> Martin
>
>
>
>
>
> ----- Original Message -----
> From: "Vladimir Obradovic" <lepiaf na bgwireless.net
> <mailto:lepiaf na bgwireless.net>>
> To: "ronja-request na lists.pointless.net
> <mailto:ronja-request na lists.pointless.net>"<ronja na lists.pointless.net
> <mailto:ronja na lists.pointless.net>>
> Sent: Thursday, February 21, 2008 1:35 AM
> Subject: Re: [Ronja] What is holding back 100 mbps
>
>
> >
>
> >> From: "CD930" <cd930 na centrum.cz <mailto:cd930 na centrum.cz>>
> >> I tested on MAXIM and MARVELL chip-set....
> >> http://www.youtube.com/watch?v=9h3hDm32kv4
> >> http://www.youtube.com/watch?v=YcjaJhMHcNk
> >
> >> TX can by IR-LED, but with short peak to 1ns......
> >> http://www.roithner-laser.com/LED_MID_IR.htm or
> >> http://www.roithner-laser.com/LED_HP_single_chip.html
> >
> >> I am after tested go to laser diode, it is simply.
> >> Martin
> >
> > Nice demo Martin, is there some chance that documentation, tips or
> > howtos be available about this project some time in future? Anyplans
> > for some kind of open hardware licence like Ronja is, or it will be
> > yet another of those projects that inherit Ronja's ideas/hw,
> showsome
> > good
> > stuff and then go into some factory for big bucks only :) ? Nowonder
> > why Cl always gets upset when ppl start asking about 100mbps orxtra
> > range versions :)
> >
> > cya
> > LePiaf
> >
> >
> > --
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> >
> >
>
>
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