SlideshowCableLabs Gives Optical Fiber a Massive Efficiency Boost

CableLabs illustration of Full Duplex Coherent Optics
CableLabs illustration of Full Duplex Coherent Optics

comtech3 3/10/2018 | 4:52:52 AM
Cablelabs Now hold on, and pardon my ignorance. Cablelabs is sending out mix signals(pun intended) here. First they're working on DOCSIS 3.1 symmetrical downstream/upstream signalling methods, while on the same token they're in an advance stage in implementing this scheme that uses the same wavelenght for both upstream/downstream with some kind of mixer. That to my knowledge, is akin to a resonant circuit.

My question is. What technique is used by say, Verizon Fios, to achieve symmetrical upstream/downstream? is Fios using two fibers with the same wavelenght to bring about that outcome? Another thing. Unless there is a massive construction boom where new greenfield homes are going to be built, I don't forsee  large investment in fiber extending beyond the backhaul. Maybe to businesses and enterprise customers, and to compliment and supplement cell towers and millimeter wave, but not residential customers.

Another thing is, ISPs will have to pump more money on top of what they have already invested in headend gears, in addition to replacing existing node circuit boards. That is costly, and entails denying customers their services while those upgrades takes place.
maurelius 3/10/2018 | 10:02:44 AM
Re: Cablelabs AT&T has shown a willingness to invest in fiber to the home for residences that are easily served by aerial. They're also doing FTTH for greenfield builds, and there's a natural amount of greenfield every year, provided we're not in a recession.

There's a significant number of customers in the Midwest who have copper in the ground - I haven't heard that AT&T is doing the expensive work of trenching/acquiring permits to serve these customers with FTTH. There's only state I know of that this has occurred in, and it's because that particular state has Google Fiber and Comcast competing with it - Georgia. You can do some Googling and find this on DSLreports.com

ATT is claiming they will pass (that can order FTTH service) 17 million homes/businesses by the end of next year - if you believe them (there's really no way to validate their claims).

The two initiatives you've identified are separate engineering projects. I can't answer your claim with respect the fiber using the same wavelength with a mixer.

Cables biggest expense in the coming years will be transitioning all the equipment on their line to n+0 - fiber to a coax splitter, _without_ any amps in the loop. You can't go symmetrical DOCSIS 3.1 without being n+0.
comtech3 3/11/2018 | 6:50:28 AM
Re: Cablelabs agreed! N+0 is achievable for cablecos given that the nodes are not too far from the actives themselves, which are spaced much closer in systems with 862MHz gears, and a wee bit further away with 750MHz line extenders.Essentally, extending fiber, and installing fiber taps shouldn't be a whole day affair that would factor in the labor cost on a hourly basis. It is the cumulative labor cost for an entire system that has over 70k subs that MAY seem cost-prohibitive. However, it is my opinion that running fiber based on the homes passed is now almost the same as running hardline coax, which possibly amounts to $500/homes passed.

If that figure is correct, or say, $750, cable MSOs are still squeezing every single digital blood out of their hardline coax,and are simply wasting money on a moribun plant (HFC) that is costly to keep on life support! Consider that they have to pay the electric companies to power their plant. Pay a lot in overtime for their maintenance technician for routine repairs, and power outages and plant breakages. With straight up fiber,the cost reduction is significant, and with the POSSIBILITY of passing on that savings to subscribers.

majortom1981 3/12/2018 | 8:04:31 AM
Re: Cablelabs First off fios doesn't have symetrical on their ftth. They just have the speeds low enough to have symetrical.  gpon is 2.4Gbits down and 1.2Gbits up. 


Also from what I understand this is to allow symetrical down and up from the headend to the node on 1 fiber. Right now it uses 2 one fiber for down and 1 fiber for up. 


This would allow cable companies to have better use of the fiber they do have in the field. 
comtech3 3/12/2018 | 10:40:21 AM
Re: Cablelabs The last time I checked, the word symmetrical means the same symetry in mathematical terms, and iso and homogenous for chemistry and biology respectively. Are we going to play pun on words? Fios has the ability to give 75/75, 100/100, or 500/500, download and upload throughput. Aren't those values symmetrical?

This simply tells me that Fios may be using the same 1550 nano wavelenth in both directions to acheive that, or some fancy modulation scheme.
majortom1981 3/12/2018 | 10:49:59 AM
Re: Cablelabs Total bandwidth on the gpon node (so to speak) is not symetrical. IF you give people above 1 gigabit it will be 2.4/1.2 Thats not symetrical.
comtech3 3/12/2018 | 11:32:04 AM
Re: Cablelabs You're one confused person! BW  is not the same as throughput. 2.4/1.2, is not the same as BW. Those are throughput, commonly called speed of transmission. BW is  the range of frequencies of a particular RF transport medium. Example of this is, 17- 862MHz for CATV ISPs, or 600-1400MHz  frequencies for cell phone providers. Again, what is 75/75 and 100/100 that Fios offers to its subs? aren't those symmetrical speeds, or some kind on misnomer/
JackZhuhong 3/12/2018 | 11:51:02 PM
FDX in coax, not fiber The FDX is in coax, which through crosstalk cancellation to send signal in both direction over the same frequency band. It needs N+0 and DAA.

In fiber, it's still seperate wavelength for up/down  in one fiber. Eg. XGS PON uplink for CMC to achieve both 10G in up/down.
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