From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from MAIL1.WPI.EDU (MAIL1.WPI.EDU [130.215.36.91]) by huchra.bufferbloat.net (Postfix) with ESMTP id C144721F2B0 for ; Fri, 12 Sep 2014 19:48:44 -0700 (PDT) Received: from MAIL1.WPI.EDU (MAIL1.WPI.EDU [130.215.36.91]) by MAIL1.WPI.EDU (8.14.9/8.14.9) with ESMTP id s8D2mg0A020428; Fri, 12 Sep 2014 22:48:42 -0400 X-DKIM: Sendmail DKIM Filter v2.8.3 MAIL1.WPI.EDU s8D2mg0A020428 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=wpi.edu; s=_dkim; t=1410576522; bh=+FgoEVbu9d5AaDlgAsAZaHrNjdX4puE334VD+t/VDuw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:In-Reply-To; b=HXg8jyyfP8PjMSk9QEzEuaI5aUwuajAph3nlx4plGi2/hcB1BMRuhlel56r0dXN2t Y4W2M4/55qtqHvHSvB5tB/brbbFjYLXVSFIfcLArrzzs8na5FVRv/wV2n0FjIs1SLu njTZx9sU3QZ0GoHWKvi7giq0VZp++AHhW6+SYmSE= Received: from MX1.WPI.EDU (mx1.wpi.edu [130.215.36.141]) by MAIL1.WPI.EDU (8.14.9/8.14.9) with ESMTP id s8D2mgkK020425; Fri, 12 Sep 2014 22:48:42 -0400 Received: from angus.ind.WPI.EDU (ANGUS.IND.WPI.EDU [130.215.130.21]) by MX1.WPI.EDU (8.14.4/8.14.4) with ESMTP id s8D2meo2021356; Fri, 12 Sep 2014 22:48:41 -0400 (envelope-from cra@WPI.EDU) Received: from angus.ind.WPI.EDU (localhost [127.0.0.1]) by angus.ind.WPI.EDU (8.14.4/8.14.4) with ESMTP id s8D2me41031298; Fri, 12 Sep 2014 22:48:40 -0400 Received: (from cra@localhost) by angus.ind.WPI.EDU (8.14.4/8.14.4/Submit) id s8D2meUA031297; Fri, 12 Sep 2014 22:48:40 -0400 X-Authentication-Warning: angus.ind.WPI.EDU: cra set sender to cra@WPI.EDU using -f Date: Fri, 12 Sep 2014 22:48:40 -0400 From: Chuck Anderson To: Dave Taht Message-ID: <20140913024839.GU15839@angus.ind.WPI.EDU> Mail-Followup-To: Dave Taht , cerowrt-devel@lists.bufferbloat.net References: <1410377469.392315248@apps.rackspace.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-12-10) Cc: cerowrt-devel@lists.bufferbloat.net Subject: Re: [Cerowrt-devel] 10GigE nics and SFP+ modules? X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 13 Sep 2014 02:49:13 -0000 > thank you all for sharing your knowledge! > > In my life I've punched holes in coax, run arcnet, climbed mountains > and tall buildings to run wifi P2P links and cut and crimped more > twisted pair than I care to remember, but my exposure to fiber's > methods has been sadly limited, til now. > > I still don't quite have a grip on how and when to use various forms > of cwdm or what wavelengths make the most sense, when... "Normal" optics (sometimes called "grey") run at the standard wavelength defined for whatever standard they are made for, for example 1000BASE-SX runs at 850nm over multimode fiber, and 1000BASE-LX runs at 1310nm over singlemode fiber. Similarly, 10GBASE-SR is 850nm and 10GBASE-LR is 1310nm. These are the commonly available wavelengths and would be what you would normally use unless you have a specific reason to do otherwise. You use CWDM or DWDM "colored" optics when you have a scarcity of fiber strands and you need/want to run multiple signals or links across them. For example, for metro fiber or long haul fiber, you get charged by how many strands you lease and how long the run is. With cheap passive CWDM or DWDM multiplexers, you can run multiple 1gig or 10gig Ethernet links across just 2 strands of metro fiber, or even a single strand with "bidirectional" optical modules which use a different wavelength for each direction. As another example, if you want to run Fibre Channel alongside Ethernet over the same strands you can also do that with WDM. Longer haul links may require more sophisticated active WDM gear and amplifiers and can get very expensive. Historically, these active WDM systems also had (and may still have) "transponders" to convert from the standard "grey" wavelengths 850nm or 1310nm installed in the routers/switches to the WDM wavelengths used on the WDM links. It is becoming more common though to forego the expense of the transponders and instead install the WDM optics directly into the routers & switches via removeable SFP (1gig - 4gig) or SFP+ (8gig, 10gig) modules. The C in CWDM stands for Coarse, and the spectrum is divided into 4, 8, or less commonly 16 wavelengths, from 1270nm to 1610nm. Here is a good pictorial: http://a2net.eu/images/dwdm.gif The D in DWDM means Dense, and there are 40, 80, or more wavelengths much more tightly packed together, usually wholly within the 1550nm band. More here: http://a2net.eu/en/solutions-fiberoptics/