Although single mode fiber (SMF) and multimode fiber cable (MMF) are widely
used in diverse applications, the problem about differences between single mode
fiber and multimode fiber is still confusing. Therefore, the following article
will focus on the basic construction, fiber distance, cost, fiber color, etc.,
to make an in-depth comparison between single mode and multimode fiber.
Overview of Single Mode vs Multimode Fiber
Single mode means the fiber enables one type of light mode to be propagated
at a time. While multimode means the fiber can propagate multiple modes. The
differences between single mode and multimode fiber mainly lies in fiber core
diameter, wavelength & light source, bandwidth, color sheath, distance and
cost.
Core Diameter
Single mode fiber core diameter is much smaller than multimode fiber. Its
typical core diameter is 9 µm even if there are others available. And multimode
fiber core diameter is 50 µm and 62.5 µm typically, which enables it to have
higher "light gathering" ability and simplify connections. The
cladding diameter of single mode and multimode fiber is 125 µm.
The attenuation of multimode fiber is higher than SM fiber because of its
larger core diameter. The fiber core of single mode cable is very narrow, so
the light that passes through these fiber optical cables is not reflected too
many times, which keeps the attenuation to a minimum.
9/125 Single Mode Fiber Simplex |
50/125 OM3 Multimode Fiber |
||
Attenuation at 1310nm |
0.36 dB/km |
Attenuation at 850 nm |
3.0 dB/km |
Attenuation at 1550nm |
0.22 dB/km |
Attenuation at 1300 nm |
1.0 dB/km |
Wavelength & Light
Source
Due to the large core size of multimode fiber, some low-cost light sources
like LEDs (light-emitting diodes) and VCSELs (vertical cavity surface-emitting
lasers) that works at the 850nm and 1300nm wavelength are used in multimode
fiber cables. While the single mode fiber often uses a laser or laser diodes to
produce light injected into the cable. And the commonly used single mode fiber
wavelength is 1310 nm and 1550 nm.
Bandwidth
Multimode fiber bandwidth is limited by its light mode and the maximum
bandwidth at present is 28000MHz*km of OM5 fiber. While single mode fiber
bandwidth is unlimited theoretically because it allows only one light mode to
pass through at a time.
Color Sheath
According to the TIA-598C standard
definition, for non-military applications, single mode cable is coated with
yellow outer sheath, and multimode fiber is coated with orange or aqua jacket.
Find more details about the Fiber Optic Cable Color Code here.
Single Mode vs
Multimode Fiber Distance
It’s known that single mode fiber is suitable for long-distance
applications, while multimode optical fiber is designed for short-distance
runs. Then when it comes to single mode vs multimode fiber distance, what’s the
quantifiable differences?
Fiber Optic Cable Type |
Fiber Cable Distance |
|||||||
Fast Ethernet 100BA SE-FX |
1Gb Ethernet 1000BASE-SX |
1Gb Ethernet 1000BA SE-LX |
10Gb Base SE-SR |
25Gb Base SR-S |
40Gb Base SR4 |
100Gb Base SR10 |
||
Single mode fiber |
OS2 |
200m |
5,000m |
5,000m |
10km |
/ |
/ |
/ |
Multimode fiber |
OM1 |
200m |
275m |
550m (mode conditioning patch cable
required) |
/ |
/ |
/ |
/ |
OM2 |
200m |
550m |
/ |
/ |
/ |
/ |
||
OM3 |
200m |
550m |
300m |
70m |
100m |
100m |
||
OM4 |
200m |
550m |
400m |
100m |
150m |
150m |
||
OM5 |
200m |
550m |
300m |
100m |
400m |
400m |
From the chart, we can see that single mode fiber distance is much longer
than that of multimode fiber cables at the data rate from 1G to 10G, but
OM3/OM4/OM5 multimode fiber supports a higher data rate. Because multimode
optical fiber has a large core size and supports more than one light mode, its
fiber distance is limited by modal dispersion which is a common phenomenon in
multimode step-index fiber. While single mode fiber is not. That’s the
essential difference between them. In addition, OS2 single mode fiber could
support longer distances in 40G and 100G links, which is not listed in the
table.
Single Mode vs
Multimode Fiber Cost
“Single mode vs multimode fiber cost” is a hot topic in some forums.
Numbers of people have expressed their own opinions. Their views mainly focus
on the optical transceiver cost, system cost and installation cost.
Optical Transceiver Cost
Compared to single-mode transceivers, the price of multimode transceivers
is nearly two or three times lower. The following table takes FS.COM Cisco
compatible single-mode transceivers and multimode transceivers as an example.
Speed |
Transceiver |
Transceiver Description |
Price |
Price Difference |
1G |
Cisco GLC-LH-SMD Compatible 1000BASE-LX/LH SFP 1310nm 10km DOM
Transceiver |
US$ 7.00 |
US$ 1.00 |
|
Cisco GLC-SX-MMD Compatible 1000BASE-SX SFP 850nm 550m DOM Transceiver |
US$ 6.00 |
|||
10G |
Cisco SFP-10G-LR Compatible 10GBASE-LR SFP+ 1310nm 10km DOM Transceiver |
US$ 24.00 |
US$ 6.00 |
|
Cisco SFP-10G-SR Compatible 10GBASE-SR SFP+ 850nm 300m DOM Transceiver |
US$ 24.00 |
|||
25G |
Cisco SFP-25G-LR-S Compatible 1310nm 10km |
US$ 59.00 |
US$ 20.00 |
|
Cisco SFP-25G-SR-S Compatible 850nm 100m |
US$ 39.00 |
|||
40G |
Cisco QSFP-40G-LR4 Compatible 40GBASE-LR4 and OTU3 QSFP+ 1310nm 10km LC
DOM Transceiver |
US$ 279.00 |
US$ 240.00 |
|
Cisco QSFP-40G-SR4 Compatible 40GBASE-SR4 QSFP+ 850nm 150m MTP/MPO DOM
Transceiver |
US$ 39.00 |
|||
100G |
QSFP28 Cisco QSFP-100G-LR4-S 100GBASE-LR4 1310nm 10km Compatible
Transceiver |
US$ 499.00 |
US$ 400.00 |
|
QSFP28 Cisco QSFP-100G-SR4-S Compatible 100GBASE-SR4 850nm 100m
Transceiver |
US$ 99.00 |
From the table, we can see that the price difference gains greatly with the
speed increasing.
System Cost
To utilize the fundamental attributes of single mode fibers, which are
generally geared towards longer distance applications, requires transceivers
with lasers that operate at longer wavelengths with smaller spot-size and
generally narrower spectral width. These transceiver characteristics combined with
the need for higher-precision alignment and tighter connector tolerances to
smaller core diameters result in significantly higher transceiver costs and
overall higher interconnect costs for single mode fiber interconnects.
Fabrication methods for VCSEL based transceivers that are optimized for use
with multimode fibers are more easily manufactured into array devices and are
lower cost than equivalent single-mode transceivers. Despite the use of
multiple fiber lanes and multi-transceivers arrays, there are significant cost
savings over single-mode technology employing single or multichannel operation
over simplex-duplex connectivity. Multimode fiber system offers the lowest
system cost and upgrade path to 100G for standard-based premises applications
using parallel-optic based interconnects.
Installation Cost
Single-mode optical fiber often costs less than multimode fiber. When
building a 1G fiber optic network that you want to be able to go to 10G or
faster on eventually, the savings on cost of fiber for single-mode saves about
half-price. While the multimode OM3 or OM4 fiber increases 35% in cost for SFP
modules. The single-mode optics are more expensive, but the labor costs of
replacing the multimode are significantly higher, especially if that followed
OM1—OM2—OM3—OM4. If you are willing to look at used ex-Fibre Channel SFPs, the
price of single-mode 1G drops through the floor. If you have the budget and
need for 10G short connections, the economics at last check still support
multimode. Keep an eye on those economics though, as history suggests that the
price premium for single-mode will drop.
Frequently Asked Question about Single Mode vs Multimode Fiber
Q: What is better single mode or
multimode fiber?
A: As has mentioned above, single mode fiber and multimode fiber cable have
their own advantages on cost and applications. There is no such thing that
single mode optical fibers are better than multimode ones. Just choosing the
best-fit one for your applications is ok.
Q: Can I mix single mode and multimode
fiber?
A: This answer for this question is “no”. Multimode fiber and single mode
fiber have different core sizes, and the number of light modes that they
transmit is also different. If you mix the two fibers, or connect them together
directly, you’ll lose a large amount of optical loss, resulting in a link
flapping or being down. Keep in mind that never mix different types of cabling
randomly.
Q: Can I use a multimode transceiver on
single mode fiber?
A: Generally speaking, the answer is "no". Large optical loss
will occur if a multimode transceiver is connected with single mode fiber.
However, the opposite will work. For example, 1000BASE-LX single mode SFP can
work on multimode fiber cable by using mode conditioning fiber cable.
Sometimes, fiber media converters also can be used to solve such problems
between single mode transceivers and multimode transceivers.
Q: Single mode vs multimode Fiber: which
should I choose?
A: When making a decision between single mode and multimode fiber cables,
the first factor to consider is the fiber distance which you need actually. For
example, in a data center, multimode fiber cables are enough for the distance
of 300-400 meters. While in applications that require distance up to several
thousands of meters, the single mode fiber is the best choice. And in
applications that can use single mode and multimode fiber, other factors like
cost and future upgrade requirements should be taken into consideration for
your choice.
Summary
From the comparison—single mode vs multimode fiber, it can conclude that
both single-mode optics and multimode optics have their own features.
Single-mode fiber cabling system is suitable for long-reach data transmission
applications and widely deployed in carrier networks, MANs and PONs. Multimode
fiber cabling system has a shorter reach and is widely deployed in enterprise,
data centers and LANs. No matter which one you choose, on the basis of total
fiber cost, choosing the one that best suits your network demands is an
important task for every network designer.
source : https://community.fs.com/blog/single-mode-cabling-cost-vs-multimode-cabling-cost.html
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