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Fiber General |
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Do I need to be concerned with PMD (Polarization
Mode Dispersion) when designing my fiber network? |
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PMD needs to be addressed for systems operating at
10 Gbps, OC-192 or STM-64 and higher.
Posted May 8, 2005 |
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What is the most accurate method of measuring
total fiber cable loss? |
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The best method of measuring fiber
optic loss is with a power meter and source and not
an OTDR. OTDRs are great for viewing anomalies along
a fiber span but do not have the ability to measure
accurate end to end fiber loss. For an accurate end
to end fiber loss measurement, a calibrated optical
power meter and source need to be used. For
single mode fiber a laser source needs to be used.
If DWDM wavelengths are to be deployed in the fiber,
then optical power measurements should be made at
those DWDM wavelengths, or use the DWDM source
itself as a test source. This is because optical
fiber loss varies with wavelength. In addition
the optical power measurement should be made in the
same direction as the transmission system.
Measurements in both directions will result in
slightly different readings. Also, all fiber
connections need to be clean, including the
connections on the test equipment.
Posted Apr 17, 2005 |
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How many fibers are
required for full duplex communications between two
nodes? |
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Generally two fibers, one fiber for
traffic transmission in each direction.
However, by using DWDM,
WDM or
Bi-directional coupler technology,
it may be possible to reduce this to one fiber.
Posted Mar 27, 2005 |
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How can I increase my existing fiber bandwidth
(traffic capacity) economically? |
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There are a number of different ways. To
economically double your fiber capacity, you may be able to use
Bi-directional couplers that allow traffic
transmission in both directions on one fiber.
Installing of Bi-directional couplers does not
require end node equipment to be modified.
To further increase
capacity, you may be able to install passive,
Cross Band WDMs,
DWDMs, or CWDMs.
Cross band WDMs double fiber capacity by combining
1310 and 1550 nm wavelengths onto
one fiber. Your nodes must be equipped with
1310nm and 1550nm lasers.
DWDMs significantly
increase fiber bandwidth by combining from 2 to 32
wavelengths onto one fiber.
However to use DWDMs end node equipment must be
equipped with proper DWDM ITU-T lasers.
CWDMs can also
be used to increase fiber capacity by combining 2 to
16 wavelengths onto
one fiber. CWDM lasers need to be used at node
equipment.
Posted Mar 27, 2005 |
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What are the maximum
number of wavelengths that can be placed onto a
fiber using DWDMs? |
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Depends on the equipment manufacturer technology, but
presently can be anywhere from 4 to 80 wavelengths.
Posted Mar 27, 2005 |
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How do you decided between optical amplifier and
repeater? |
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The decision is
made during engineering design of the fiber
network. In general, optical amplifiers, such as
EDFA, are used to boost the optical signal to
compensate for link optical loss. They do not
recondition the signal. Repeaters are used also to
boost an optical signal but in addition they are
used to clean the sign up, recondition the
signal, to allow for longer transmissions. Most but
not all repeaters are 3R type, they re-amplify
(boost signal), re-shape (removes pulse
distortions), and re-time (removes timing jitter to
improve clock recovery) the received optical signal. |
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If wavelength one is 2 dBm, wavelength two is 4 dBm
and wavelength three is 6 dBm, then when multiplexed
and send through DWDM what will be the optical power
after multiplexing? |
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The
total power will be the sum of the individual
wavelength powers in mW less the DWDM insertion
loss. So for this case 2 dBm= 1.58 mW, 4 dBm=2.51
mW, and 6 dBm=3.98 mW . The total power out of the
DWDM is Sum = 8.07 mw or 9.1 dBm less the DWDM
insertion loss. |
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SONET/SDH
Equipment |
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I have run
out of capacity on my present SONET system and do
not have any spare fibers to add a
parallel system. Can I install DWDMs without
affecting my current system's traffic? |
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Upgrades to a live SONET/SDH system is
possible and does not require circuit down time. Using SONET/SDH
protection switching proper DWDM equipment can be
added without circuit down time.
Posted Mar 27, 2005 |
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I need to
reach a number of customers with DS3 and Ethernet
circuits but I do not have the budget to
use costly SONET equipment. Any Suggestions? |
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Try pricing your project with refurbished SONET equipment.
Refurbished
equipment can be as much as 85% off list price
and carries excellent replacement warranties.
Posted Mar 27, 2005 |
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How far apart can
SONET/SDH nodes be placed? |
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This questions depends on many factors including
type of SONET/SDH equipment,
transmission rate, OSP optical fiber type,
total optical budget and dispersion. A
detailed design needs to be conducted to determine
permissible fiber cable distances. Using
optical
amplifier technology it may be possible to
extend distances between nodes to over 170 km (110
mi).
Posted Mar 27, 2005 |
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Are there any alternatives to SONET/SDH Ring and Linear
protection? |
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Yes, try protecting your SONET/SDH system using Mesh Protected Networks.
Mesh Protected Networks allows for alternate
protection paths in a network.
Posted Mar 27, 2005 |
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Multi-mode VS Singlemode
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My fiber system uses
multi-mode fiber. Can I increase multi-mode
fiber capacity using WDM or DWDM technology? |
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No, WDM and DWDM technology is not available for
multi-mode fiber.
Posted Mar 27, 2005 |
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Can multi-mode and singlemode equipment be
interchanged? |
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Generally No, multi-mode and singlemode equipment
and fiber are not interchangeable and not
compatible.
Posted Mar 27, 2005 |
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