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This FAQ is edited by: redxii See Profile, Oxygen See Profile
It was last modified on 2005-07-25 22:30:12


What's the purpose of the Fiber Optic Forum?

The Fiber Optic Forum is for discussions of internet access through fiber optic transmission and issues of availability, types of service, and obstacles to deployment and other services "hidden behind fiber".

How do I add to this FAQ?

Click here to submit questions or information to this FAQ. It will be reviewed and if accepted will appear here soon.

1. General Questions

What are Fiber Optics?

Fiber optics (optical fibers) are long, thin strands of very pure glass about the diameter of a human hair. They are arranged in bundles called optical cables and used to transmit light signals over long distances.

If you look closely at a single optical fiber, you will see that it has the following parts:

Core - Thin glass center of the fiber where the light travels.
Cladding - Outer optical material surrounding the core that reflects the light back into the core.
Buffer coating - Plastic coating that protects the fiber from damage and moisture.
Hundreds or thousands of these optical fibers are arranged in bundles in optical cables. The bundles are protected by the cable's outer covering, called a jacket.

Optical fibers come in two types:

Single-mode fibers - Used to transmit one signal per fiber (used in telephones and cable TV)
Multi-mode fibers - Used to transmit many signals per fiber (used in computer networks, local area networks)

Single-mode fibers have small cores (about 3.5 x 10-4 inches or 9 microns in diameter) and transmit infrared laser light (wavelength = 1,300 to 1,550 nanometers). •Multi-mode fibers have larger cores (about 2.5 x 10-3 inches or 62.5 microns in diameter) and transmit infrared light (wavelength = 850 to 1,300 nm) from light-emitting diodes (LEDs).Some optical fibers can be made from plastic. These fibers have a large core (0.04 inches or 1 mm diameter) and transmit visible red light (wavelength = 650 nm) from LEDs.

"How Fiber Optics Work", HowStuffWorks
www.howstuffworks.com), by Craig C. Freudenrich, Ph.D.
HowStuffWorks, Inc., 2002.

Advantages of Fiber Optics

Compared to conventional metal wire (copper wire), optical fibers are:
Less expensive - Several miles of optical cable can be made cheaper than equivalent lengths of copper wire. This saves your provider (cable TV, Internet) and you money.
Thinner - Optical fibers can be drawn to smaller diameters than copper wire.
Higher carrying capacity - Because optical fibers are thinner than copper wires, more fibers can be bundled into a given-diameter cable than copper wires. This allows more phone lines to go over the same cable or more channels to come through the cable into your cable TV box.
Less signal degradation - The loss of signal in optical fiber is less than in copper wire.
Light signals - Unlike electrical signals in copper wires, light signals from one fiber do not interfere with those of other fibers in the same cable. This means clearer phone conversations or TV reception.
Low power - Because signals in optical fibers degrade less, lower-power transmitters can be used instead of the high-voltage electrical transmitters needed for copper wires. Again, this saves your provider and you money.
Digital signals - Optical fibers are ideally suited for carrying digital information, which is especially useful in computer networks.
Non-flammable - Because no electricity is passed through optical fibers, there is no fire hazard.
Lightweight - An optical cable weighs less than a comparable copper wire cable. Fiber-optic cables take up less space in the ground.
Because of these advantages, you see fiber optics in many industries, most notably telecommunications and computer networks.


What does it cost to use fiber vs. conventional cat 5 cabling for a LAN?

Fiber will cary any speed imaginable its not limited, and CAT5 carries only 100 mbit. The expense is about 1000 times CAT5 for fiber. It's VERY expensive to lay fiber. We are talking low 6 figures per about 100 feet of cable. Typical cost of multimode fiber per foot is around $0.75 compared to $0.10 for Cat5e Gigabit certified copper cable.

Thanks to:

FTTB, FTTC, FTTH, and FTTN technologies

"Fiber to the Building" (FTTB) refers to installing optical fiber from the telephone company central office to a specific building such as a business or apartment house.

"Fiber to the Curb" (FTTC) refers to the installation and use of optical fiber cable directly to the curbs near homes or any business environment as a replacement for "plain old telephone service" (POTS) Fiber to the curb implies that coaxial cable or another medium might carry the signals the very short distance between the curb and the user inside the home or business.

"Fiber to the Home" (FTTH) is a network technology that deploys fiber optic cable directly to the home or business to deliver voice, video and data services. By leveraging the extremely high bandwidth capacity of fiber, FTTH can deliver more bandwidth capacity than competing copper-based technologies such as twisted pair, HFC and xDSL.

Fiber to the home is deployed in two primary architectures - point-to-point and passive optical network (PON). While both have their place in solving the last-mile bottleneck, a point-to-point architecture is generally deployed to businesses in metro and urban areas, while a PON is a more cost-effective solution for small- to medium-sized businesses and residences. A PON architecture allows a single fiber from the central office (CO) or headend to be split up to 32 ways, delivering high-bandwidth converged services to multiple residences or businesses, using a single optical transceiver in the CO. In a point-to-point configuration, an optical transceiver for each subscriber is required in the CO, thus substantially increasing the total cost of deployment.
"Fiber to the neighborhood" (FTTN) refers to installing it generally to all curbs or buildings in a neighborhood. Hybrid Fiber Coax (HFC) is an example of a distribution concept in which optical fiber is used as the backbone medium in a given environment and coaxial cable is used between the backbone and individual users (such as those in a small corporation or a college environment).

Source/Reference (2)

DFITL, IFITL and FITL technologies


DFITL is in short adsl over FITL (fiber in to loop/fiber to the curb). The way it works is it sends the dsl signal over fiber to the ONU thur the DISCS system and connects to the ATM in the CO. The card in the ONU acts like the DSLAM since the signal runs over copper from the ONU to the house.
by fiber_man

IFITL is an implementation of FTTC by Marconi Communications which delivers integrated voice, Digital TV, and high-speed data (PCDATA).

PCDATA which is simply 10Mbps Ethernet delivered to your doorstep. You can't buy "PCDATA" itself because there are no tarrifs for that class of service. Instead Bellsouth sells a throttled version (1.5Mbps down/ 256Kbps up) of PCDATA as "Fast Access". Some call this "DSL over Fiber", but this is a misnomer as there is no DSL signalling involved at all...it's Ethernet, period.

FITL = IFITL without the video and data services (e.g. no PCDATA).

If you are in the unfortunate circumstance of being located in a sub-division serviced by FITL, you are ironically, at a major disadvantage. Remember, DSL requires copper cabling, a DSL modem in your home AND a DSL modem on the other end of the copper (a DSLAM). Since FITL pushes fiber to the curb, the only copper that exists is between your home and the pedestal....and their ain't no DSLAMS in the pedestals.

What is Hybrid Fiber Coax (HFC)?

Hybrid Fiber Coax is a way of delivering video, voice telephony, data, and other interactive services over coaxial and fiber optic cables.

An HFC network works consists of a headend office, distribution center, fiber nodes, and network interface units.

The headend office receives information such as television signals, Internet packets, and streaming media, then delivers them through a SONET ring to distibution centers. The distribution centers then send the signals to neighborhood fiber nodes, which convert the optical signals to electrical signals and redistributes them on coaxial cables to residents' homes where network interface units send the appropriate signals to the appropriate devices (i.e. television, computer, telelphone).

An HFC network provides the necessary bandwidth for home broadband applications, using the spectrum from 5 MHz to 450 MHz for conventional downstream analog information, and the spectrum from 450 MHz to 750 MHz for digital broadcast services such as voice and video telephony, video-on-demand, and interactive television.


What is SONET?

SONET is Synchronous Optical NETworking. SONET equipment generally uses one wavelength, or lambda, to carry an OC level (see below), which can be divided into time slots for individual circuits. SONET is generally used at the carrier level to build diverse networks to carry the Internet backbone, point-to-point leased lines, and pretty much anything else with a SONET interface (ATM & frame relay switches, voice switches, digital cross connects, other multiplexers). SONET in Europe and Asia is known as SDH (Synchronous Digital Heirarchy). Asia's SDH differs from Europe's in some respects.

SONET OC levels:
OC1 - 52mb/s
OC3 - 155mb/s
OC12 - 622mb/s
OC48 - 2.5gb/s
OC192 - 9.6gb/s
OC768 - 40gb/s

You can divide OC circuits into what are called STS channels, or tributaries. Generally each OC level has a corresponding STS level, and higher bandwidth optical equipment can carry more than one STS channel, such as a combination of any of the following:

VT-1.5 = T-1 (1.44mb/s)
VT-2 = 2mb/s
OC-1 = STS-1 (usually used for DS3/T3)
OC-3 = STS-3c or STS3 (3 STS1 channels)
OC-12 = STS-12c or STS12
OC-48 = STS-48c or STS48
OC-192 = STS-192c or STS192
OC-768 = STS-768c or STS768 (have not encountered these systems yet)

SDH equivalents:
STS-3c = STM-1
STS-12c = STM-4
STS-48c = STM-16
STS-192c = STM-64

The "c" in STS3c or OC3c stands for concatenated, meaning that the entire 155mb/s is dedicated to one channel (one payload), unlike an STS3, which would be 3 STS1 channels (3 payloads). For instance, on an OC12 ring, you could have 9 STS1 channels and 1 STS3c channel, or 3 STS3c channels and 3 STS1 channels. Once the channels are demultiplexed, they are split into tributaries, the lower-bandwidth interfaces used for connecting to other networking equipment.

Each OC level can be a ring interface to a UPSR (Unidirectional Path Switched Ring) or BLSR (Bi-directional Line Switched Ring). On these rings, generally one line goes east, and another west. If one side fails, individual STS channels (UPSR) or the entire line (BLSR) can be switched to the other path or span, depending on the technology.

2. Forum Links

Search Engine Results for Fiber Optic Internet

Research links from search engines by Bobo, can be found here.

Glossary of Fiber Optic Terms

An alphabetical list of Fiber Optic Terms can be found at FOTEC.COM.

File Download Time Calculator

Think you have a fast connection? You can compare how long it'll take approximately to download a file with many connection types--from 9600 baud modems to a 10Tbps (Terabits per second) connections--with the File Download Time Calculator.

Fiber to the Home News

3. Troubleshooting

First hop ping is really high!

When you run a line test, you may get something like this:

Your first hop ping stream of 40byte pings to xx.xx.xxx.xx
100% loss | unknown reason | You are 87ms to your first hop!
Don't be alarmed. Your ISP might have a "private domain", so you get a 100% loss with a high first hop ping.

To test your first hop, do a trace route to your favorite website in MS-DOS prompt.

tracert yahoo.com

Tracing route to yahoo.com []
over a maximum of 30 hops:

1 10 ms 10 ms 10 ms xx.xxx.xx.xxx

4. Fiber Optic Service Providers

4.1 Level 3

What does 'Level 3' mean?

The term "Level 3" comes from the layered set of protocols, or standards that are often used in the industry to describe networks. The Company's strategy generally calls for services to be provided in the first three levels of these technical specifications.

Source: Level 3
Interface and port speeds available by region:
POSOC-3, OC-12, OC-48STM-1, STM-4
Ethernet100BT, Gigabit Ethernet100BT, Gigabit Ethernet

Level 3 runs single mode fiber optic cable to the customers premise. The fiber cable can have any type of hardware on both ends.

For example:

100BT Ethernet / Gigabit Ethernet:

If a customer needs Gigabit Ethernet, Level 3 will have a Cisco router with a Gigabit port on their end.

The customer will have a Gigabit switch with a GBIC (Gigabit Interface Converter) connected to the fiber optic cable.

Optical Carrier Level connections and SDH:

If POS type connection is requested, expensive hardware must be used by both ends.

Level 3 will use Fujitsu Multiplexers:

The customer will need an OC level router, such as the Juniper Networks M20:

Serial Connections - DS3/T3:

The telco needs to run a dedicated DS3 circuit.

The customer needs to have a DS3 Inverse access multiplexer and a router supporting HSSI (High Speed Serial Interface).

One of the HSSI compatible routers is a Cisco 3600 Series:

Level 3 Network Maps

What does a private fiber loop look like?

Update pictures coming in a few days... =)

4.3 SwitchPoint

What is SwitchPoint Network's DSDN technology?

What is SwitchPoint Network's DSDN technology?

SwitchPoint Network's Digital Switched Data Network (DSDN) is a proven, commercially available third-generation (3G) broadband technology that enables the deployment of 100 Mega bits per second (Mbps) last-mile networks. DSDN leverages the advantages of proven indoor Ethernet Local Area Network (LAN) technology for use in large scale, outdoor residential and small business networks.

Superior in performance to second-generation last-mile technologies such as cable modem and DSL, and lower in cost than other 3G technology alternatives such as fiber-to-the-home (FTTH), DSDN combines standard fiber and Category 6 (Cat6) cable with SwitchPoint's switches, network protocols and software to provide affordable broadband Internet access with upload and download speeds of 100 Mbps.


How does DSDN work?

DSDN technology is based on proven switched Ethernet local-area networking concepts. Originating from a fiber optic network backbone, Cat6 twisted-pair cable is connected to environmentally hardened DSDN switches throughout a neighborhood. Cat6 wiring then connects the switches to a subscriber's home or business. By using standard Ethernet connections, the DSDN network does not require expensive interfaces, and can be built for far less than FTTH alternatives. To conserve bandwidth and eliminate congestion, the DSDN switches route data packets intelligently within the network. Even if a cable is cut, the intelligent path routing capabilities of the DSDN network allow it to move around the affected area to deliver reliable, continuous service. More importantly, traffic within the network maintains a speed of 100 Mbps and does not need to travel through a central office, head-end or public Internet.


How does DSDN performance compare to the performance of FTTH?

    Speed - DSDN is commercially deploying 100 Mbps, testing 1 Gbps and
    working on 10 Gbps. Most proposed fiber deployments currently provide only 10
    Mbps to the end user.
    Scalability - Both FTTH and DSDN can scale and have robust
    architectures that are full duplex and switched. Ethernet is an extremely robust
    system for data transfer, whether through FTTH or DSDN.
    Redundancy - DSDN intelligently re-routes network traffic around any
    accidental cable cuts or path disruptions resulting in uninterrupted service to
    the consumer. Most FTTH systems are home-run strands from either the NOC or a
    major hub to the home. It takes either intelligent components in the field
    (DSDN), or redundant home run fiber from a second location (very expensive) to
    achieve redundancy.
    Ease of Implementation and Maintenance - DSDN is easier to implement
    and maintain and does not require additional customer premise equipment. FTTH
    implementations are more difficult and require special handling for each fiber
    drop to the home and the installation and maintenance of active optical
    switching equipment at the customer's premise. Cable cuts on a DSDN network are
    easy and inexpensive to locate and repair. A cut to fiber requires expensive
    equipment to locate the cut and extensive labor and equipment to repair.

How fast is DSDN compared to alternative broadband access solutions?

DSDN provides symmetrical, full-duplex 100 megabits per second bandwidth. This is at least 2,000 times faster than a dial-up modem, 14 times faster than the maximum speed of most DSL lines and ten times faster than the maximum speed of a standard cable modem.


What are the primary benefits of SwitchPoint's DSDN technology?

    100 Mbps Speed - DSDN provides symmetrical, full-duplex
    broadband access of at least 100 Mbps. This is at least 2,000 times faster than
    a 56 Kbps dial-up modem, 14 times faster than the maximum speed of DSL, and ten
    times faster than today's maximum speed of a cable modem.
    Low Cost - Deployment costs for DSDN are comparable to less
    robust second-generation alternatives and significantly less expensive than
    comparable FTTH solutions. DSDN technology delivers the performance of FTTH
    without the high cost of installing fiber optic cable to the subscriber's
    premises. While FTTH deployments can cost in excess of $3,000 per home, DSDN can
    be deployed for under $1,000 per home passed.
    Proven - The SwitchPoint DSDN solution has been in commercial
    operation more than two years and has provided broadband services to thousands
    of customers. SwitchPoint deployed DSDN to more than 10,000 homes and 2,000+
    customers in two test markets in Utah and is now marketing DSDN to network
    builders and operators.
    Upgradeable - DSDN is engineered for upgrades to 1 Gbps with a
    simple DSDN switch replacement; no new cable or construction is required. DSDN
    can cost effectively scale to deliver multi-gigabit bandwidth performance that
    matches FTTH, at a fraction of the cost.
    Scalable - DSDN networks will scale to support any number of
    homes covering a market of any size and are compatible with Metropolitan Area
    Networks (MAN) for their backbone traffic.
    Flexible - The SwitchPoint DSDN solution is extremely flexible
    and can be deployed as a stand-alone 100 Mbps data network or as an overlay to
    new or existing HFC cable networks or power grids.
    Deterministic - Each user in the DSDN network is connected to
    an individual 100 Mbps port on the closest DSDN switch and do not share their
    ports with other users on the network. The fully switched nature of DSDN
    architecture maximizes available bandwidth and guarantees performance for users.
    Flat, non-switched architectures such as cable modem networks share bandwidth
    with all users on the network, causing effective throughput to diminish at peak
    Symmetrical - DSDN provides symmetrical, full-duplex
    bandwidth, which means that users simultaneously can send and receive up to 100
    Mbps of data. In contrast, upload speeds of cable modem and DSL are
    significantly lower than their maximum download speeds preventing effective
    deployment of premium services that require symmetrical bandwidth such as
    videoconferencing, VPN and interactive gaming.
    Standards-Based - DSDN is fully compatible with standard
    Ethernet and IP protocols; works with standard networking equipment and does not
    require specialized customer premise equipment, such as a modem.
    Reliable - Neighboring DSDN nodes can be connected to each
    other through redundant Cat6 links. Even if a cable is cut, DSDN's multi-path
    routing capabilities easily work around the affected area to deliver continuous
    Secure - The DSDN network is an all-switched network. Security
    is enhanced in an all-switched network because all users on the network do not
    receive all packets. In flat network architectures such as cable modem, fixed
    wireless and some FTTH broadband platforms, this level of security is not

5. T-1 Connections

What is a T-1 connection?

A T-1 is a dedicated phone connection supporting data rates of 1.544Mbits per second. A T-1 line actually consists of 24 individual channels, each of which supports 64Kbits per second. Each 64Kbit/second channel can be configured to carry voice or data traffic. Most telephone companies allow you to buy just some of these individual channels, known as fractional T-1 access.

T-1 lines are a popular leased line option for businesses connecting to the Internet and for Internet Service Providers (ISPs) connecting to the Internet backbone. The Internet backbone itself consists of faster T-3 connections.

T-1 lines are sometimes referred to as DS1 lines.

Note: T-1 comes in either copper or fiber optics.


Checking availability in your area

To see if T-1 connections are offered in your area, check out the Classified adverts - T1/T3+ service by area map.

What is the difference between T1 and 1.5mbit SDSL?

A T1 line and an SDSL line uses the same underlying technology - HDSL. The differences between them are not in performance, they are in ease of provisioning and speed of repair.

In the US, lines for T1 data are normally treated as higher importance by telcos, than DSL lines, so time to repair and provisioning can be considerably faster. A T1 fault may be repaired within hours, or a day, whereas a DSL line fault could be a 5 day turn around time.

The other important difference is that T1 lines are more easily repeated to cover longer distances, something that has not yet happened for SDSL lines.

T1 lines are significantly more expensive than DSL lines, a monthly T1 lease, with internet bandwidth, can amount to $1000 or more, compare that with SDSL prices of a few hundred dollars for the same speed.

6. T-3 Connections

What is a T-3 connection?

A T-3 is a dedicated phone connection supporting data rates of about 43 Mbps. A T-3 line actually consists of 672 individual channels, each of which supports 64 Kbps.

T-3 lines are used mainly by Internet Service Providers (ISPs) connecting to the Internet backbone and for the backbone itself.

T-3 lines are sometimes referred to as DS3 lines.

DS3's are most often delivered via a fiber optic connection mostly an OC-3. They are split from a multiplexer (Fujitsu FLM are popular in the US). Many DS3's can be split from a single Mux.


Checking availability in your area

To see if T-3 connections are offered in your area, check out the Classified adverts - T1/T3+ service by area map.

7. Optical Carriers

What is an Optical Carrier (OC) connection?

Short for Optical Carrier, used to specify the speed of fiber optic networks conforming to the SONET standard. The table shows the speeds for common OC levels.

Optical Carrier Speed
OC-1 51.85 Mbps
OC-3 155.52 Mbps
OC-9 466.56 Mbps
OC-12 622.08 Mbps
OC-19 933.12 Mbps
OC-24 1.244 Gbps
OC-36 1.866 Gbps
OC-48 2.488 Gbps
OC-96 4.977 Gbps
OC-192 9.953 Gbps
OC-768 40 Gbps
OC-3072 160 Gbps

Each channel is 51.85 Mbps. An OC-3, for example, has 3 channels adding up to 155.52 Mbps.

Currently, Cisco CRS-1 System features OC-768 line cards. These cards are priced at $2,000,000 USD each.

What is Dense Wavelength Division Multiplexing (DWDM)?

Short for Dense Wavelength Division Multiplexing, an optical technology used to increase bandwidth over existing fiber optic backbones.

DWDM works by combining and transmitting multiple signals simultaneously at different wavelengths on the same fiber. In effect, one fiber is transformed into multiple virtual fibers. So, if you were to multiplex eight OC -48 signals into one fiber, you would increase the carrying capacity of that fiber from 2.5 Gb/s to 20 Gb/s. Currently, because of DWDM, single fibers have been able to transmit data at speeds up to 400Gb/s. And, as vendors add more channels to each fiber, terabit capacity is on its way.

A key advantage to DWDM is that it's protocol and bit-rate independent. DWDM-based networks can transmit data in IP, ATM, SONET /SDH, and Ethernet, and handle bit-rates between 100 Mb/s and 2.5 Gb/s. Therefore, DWDM-based networks can carry different types of traffic at different speeds over an optical channel.