[Cerowrt-devel] Fiber to the yurt approved

Dave Taht dave.taht at gmail.com
Tue Sep 30 18:49:31 EDT 2014

On Thu, Sep 25, 2014 at 7:53 AM, Chuck Anderson <cra at wpi.edu> wrote:
> On Thu, Sep 25, 2014 at 07:06:30AM -0700, Dave Taht wrote:
>> searching alibaba for new gear is truly an eye-opening experience...
>> examples:
>> http://www.alibaba.com/product-detail/Atheros-based-router-with-sfp-port_1979360314.html
>> http://www.alibaba.com/product-detail/Factory-OEM-Ralink-3052-300M-OpenWrt_1923358888.html
>> I am under the impression however, that SFP+ is needed for gig
>> uplinks. Not that 100Mbit
>> is bad...
> No.  SFP was originally 1 gigabit (1000 mbit) over fiber only.  Now it
> can be 100/1000 megabit dual-mode copper or fiber or 10/100/1000
> megabit tri-mode copper or fiber.  SFP+ is 10 gigabit.  There are
> other speeds as well, but those are used for things like Fibre
> Channel, SONET, ATM, etc. rather than Ethernet.
>> On Wed, Sep 24, 2014 at 11:12 PM, Joel Wirāmu Pauling <joel at aenertia.net> wrote:
>> > Put as many pairs as you can fit into the conduit to leave quite a lot of
>> > slack (2-5metres)
>> The specific question was what form of conduit (earth burial) would be sane?
>> This would be a ground burial thing where I would be comfortable with
>> ground buriable ethernet, no conduit (it's a forest), but fiber looks more
>> fragile.
>> > We bury our splitters with ofdm break outs in waterproof boxes every 500m -
>> > 2km or so for the GPON roll out and blow the Fibre to the premise from the
>> > split.
>> Residences and yurts are spaced about every 3 meters in distinct subsections.
>> > Burying splinter boxes prevents vandalism/flooding issues and
>> > accidents.
>> This is a campground in california. Amusingly, a few hours after we started
>> eagerly discussing digging up the ground, it started pouring rain. I'm going
>> to put "discuss fiber deployment" into my bag of drought-ending tricks...
>> >Con's you have to dig it up every time you want to connect
>> > another pair into the ofdm. Fibre blower kit is expensive.
>> I saw that a fiber blower box was 6k. There seem to be daily rentals
>> available...

There are also tools less expensive than a blower like these:


Too tedious and unreliable? Lord knows it's hard to crimp ground
burial cat6 gel.... takes me 6 tries every time, and if fiber is harder,
oh, my....

>> > Choose your connectors on the ofdm carefully. LC style connectors are the
>> > norm on SFP(+) optics and isn't angled. This is my personal favorite but
>> > some dislike it. Is rarely the norm for In premise kit especially for pon.
>> >
>> > Angled and unangled SC connectors are norm for PON and CPE Home kit. Angled
>> > is better for loss and used primarily on the splitter OFDM but easy to munge
>> > if you connect angled to unangled.
> Angled (APC - Angled Polish Connector) usually has a green colored
> connector, while non-angled (PC or UPC - Ultra Polished Connector)
> usually has a blue connector for singlemode.  You can't mate two
> unlike kinds (well you can try, but the loss will be high).
> Angled improves the Return Loss figure (larger negative dB value,
> usually -65 dB vs. -45 dB on regular UPC) due to it preventing
> reflections at the connector mating point from entering back into the
> trasmit fiber causing attenuation.  Instead it causes the reflections
> to divert to the side.  IME, it is used for PON and HFC networks, or
> any network that sends a RF modulated signal down the fiber.  For
> straight data-only deployments, usually un-angled is used.  Definitely
> all SFP or SFP+ modules you find will require the regular PC or UPC
> kind, not angled.
>> > You might even consider just not using a splinter or OFDM patch at all and
>> > just having slack and unterminated fibers. Cheap Chinese Fujikura equivalent
>> > spilcers can be had for around 3000$ now. And splicing is always better than
>> > patching IME.
>> >
>> > Have fun!
>> You just hit me with more condensed jargon than I've had to deal with in many
>> a month, but I think I grokked most of it. It has been really
>> interesting to absorb
>> an entirely new technology with your help, that of the list, and google.
>> First up is just to trial something between two desparately needed points...
> Outside Plant (OSP) cable is designed for outdoor use (but not
> necessarily direct-burial, may still need conduit).  There are
> regulations on how far into a building you can bring OSP cable (50 ft
> or 50 meters?) due to fire codes.  There is also Indoor/Outdoor cable
> to get around that limitation.
> Given you are using regular routers or switches, you don't want PON
> (star arrangement of fiber that passively splits to multiple
> destinations in the downstream direction, and uses timeslots for the
> upstream direction, requires special OLT and ONC gear at each end and
> isn't really regular Ethernet).  So you will generally need two
> strands for each point-to-point link (although there are special
> bi-directional SFPs you can get that will run TX and RX over a single
> strand using WDM, not recommended due to higher cost).
> Do you have a central aggregation point planned?  If so, I would
> home-run all the strands from each peripheral building to that point
> (or rather, splice separate cables together where necessary so that
> logically each building has a home run of at LEAST 2 strands, although
> I would plan on at least 6 or 12 for
> expansion/redundancy/spares/experimentation).  The labor is the
> expensive part, so pulling as many strands as possible in one go is
> the best way.  You don't have to or splice all of them or terminate
> all of them onto LC/UPC connectors yet.
> I can ask what our contractors recommend as far as type of conduit.

Dave Täht


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