1. science
2. physics
3. optics

Insertion Loss Performance Testing of 10 Gb/s Fiber Patch Cords
for High-Speed Networks
Brett Lane, Al Brunsting, Rick Pimpinella
Panduit Laboratories, Panduit Corp.
17301 South Ridgeland Avenue, Tinley Park, IL 60477
+1-708-532-1800 · [email protected], [email protected], [email protected]
Abstract
Total = 7.3 dB
Insertion loss (IL) is a critical parameter for the performance of
networks with data rates of 10 Gb/s. This paper identifies and
examines the critical parameters for making accurate and
repeatable insertion loss measurements.
Furthermore, it
compares two methods for making insertion loss measurements
(reference patch cord and random mating).
Powe r Budget (dB)
Keywords: Multimode fiber, MMF, 10 Gb/s, power budget,
launch conditions, coupled power ratio, CPR, encircled flux, EF,
reference patch cord, random mating.
1. Introduction
The performance and reliability of the data center Local Area
Network (LAN) is of paramount importance to the operation of
today’s enterprise. The specifications on the constituent
components within these networks have become more
demanding as the network performance requirements have
advanced.
For high-speed optical networks using
laser-optimized multimode fiber (MMF) operating at 10 Gb/s, it
is more critical than ever for network operators and designers to
have accurate knowledge of the performance specifications of
the active and passive fiber optic components used to make up
the network.
O
other = 0.9 dB
6
M
margin = 0.8 dB
5
4
ISI
3.0 dB (inter-symbol interference)
3
2
1
IL
1.5 dB (connectors)
+ 1.1 dB (fiber)
2.6 dB (channel)
0
Figure 1. Power budget for an optical 10 Gb/s
MMF (OM3) link.
A typical optical link within a LAN or data center may have
several patch cords connecting two pieces of network
equipment. For example, consider a core switch connected to an
access layer switch via a 10 Gb/s link (Figure 2). The access
switch transceiver transmitter may be connected to an arraybased MPO fiber cassette (FC1) via a patch cord (PC1). The
fiber cassette, FC1, may then be connected to another fiber
cassette (FC2) (establishing a permanent link) physically located
in a different area of the building.
All of the significant component limitations for 10 Gb/s networks
have been identified and quantified so that a comprehensive
network link model can be used to predict the minimum network
performance.[1] Most generally, the component limitations can be
grouped into those that are directly related to the high modulation
speeds required to support data rates of 10 Gb/s and those that are
not. Many of the laser transmitter and receiver properties are
directly related to high modulation speeds (i.e., rise/fall time, jitter,
intensity noise, etc). Additionally, the overall fiber bandwidth is
governed by dispersion effects, which become significantly more
important at high modulation speeds. Additional details on MMF
dispersion can be found elsewhere.[2, 3]
PC1
The overall optical power loss within the network, which is not
strongly related to the modulation speed, is also important for
high performance network operation. There are two sources of
optical loss, or insertion loss (IL), associated with optical
networks: 1, loss at connector-to-connector interfaces; and 2,
loss, or attenuation, within the fiber itself due to absorption and
scattering. For high performance and reliable 10 Gb/s network
operation, both of these loss sources should be minimized by
selecting high quality, low IL connectors, patch cords, and
cassettes plus high performance MMF. For 10 Gb/s networks
the maximum loss for each of these two sources has been
defined and is given in an overall power budget which is shown
schematically in Figure 1.[1] Deploying a standards compliant
network that meets or exceeds these specifications ensures costeffectiveness while retaining high performance.
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FC1
PC2
FC2
Figure 2. Schematic of a common optical link within a LAN
or data center.
Finally, the link is completed with another patch cord, PC2,
connecting FC2 to the core switch’s receiver. In this example,
the total allowable IL (not including the connections to either
transceiver) for PC1 to PC2 through FC1 and FC2 is only
2.6 dB: 1.1 dB allocated for fiber attenuation and 1.5 dB for
connector loss. The average allowable IL for these four mated
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connector pairs is 1.5 dB / 4 = 0.375 dB per pair, including the
effect of associated adapters. As more patch cords are added
within a link, each with their own pair of connectors, the total
allowable IL remains fixed at 1.5 dB while the allowable IL per
connector boundary decreases accordingly.
accuracy must be improved. Therefore, the industry requires a
newly defined launch condition that will increase the accuracy
and repeatability of IL measurements.
2.4
2.3
Channel IL (dB)
From this example it is illustrated that connector IL is a
significant parameter for the reliable operation of 10 Gb/s
networks, especially when multiple patch cords are used. It is
important therefore, that network designers and installers have
an accurate knowledge of the IL of the connectors, patch cords,
and cassettes that are being incorporated into the network.
2. Insertion Loss Launch Conditions
2.1
2.0
1.9
1.8
1.7
The most widely accepted method of measuring the IL of
multimode fiber channels and connectors is specified by
domestic and international standards. [4, 5] These standards
refer to subsequent standards applicable either to individual fiber
optic components or to cable plant systems; testing for both
requires a light source, reference launch/patch cord and
calibrated power meter.[6, 7, 8, 9] Although a nearly ideal or
‘reference’ patch cord is most commonly used as the launch
cord, sometimes the launch cord is randomly selected from the
population of components to be tested. Since it has long been
known that light sources used for IL measurements produce
various modal power distributions when launched into
multimode fiber and that multimode components posses some
level of Differential Mode Attenuation (DMA), these standards
have used the Coupled Power Ratio (CPR) parameter as a way
to specify the launch conditions at the test interface for making
accurate and repeatable IL measurements.
1.6
1.5
20
21
22
23
24
25
CPR (dB)
Figure 3. Measured IL of an optical link configured
identically to the link shown in Figure 2 (L = 312 m, OM3).
The CPR was quantified at the output of PC1.
Since the DMA of multimode cabling and connectors is largely
influenced by the power distribution at large radii, it is imperative
that the power in this portion of the fiber be tightly specified.
Unfortunately, by definition the simple CPR is not well suited for
this function and so to more precisely specify the power
distribution at large radii, another metric must be used to appraise
the modal power distribution of the light source and launch cord.
Coupled power ratio is a simple quantitative measurement of the
mode power distribution in multimode fibers. Specifically, CPR
is the ratio of the total power emitted from the multimode launch
cord fiber core to the power emitted out of a singlemode fiber
when it is connected to the distal end of the multimode launch
cord. The CPR is influenced by both the light source and launch
cord and therefore is specific to the light source and launch cord
combination. The larger the CPR, the larger fractional power at
the large radii of the fiber; conversely, the smaller the CPR, the
more power is propagating near the central region of the fiber
core. For multimode fiber channels, which inherently posses
some amount of DMA, it is generally observed that the measured
channel IL increases with light source and launch cord CPR.
3. Defining Encircled Flux
Encircled flux (EF) is a measure, as a function of radius, of the
fraction of the total power radiating from a multimode optical
fiber’s core. Since the complete mode power distribution at any
radii can be specified, it is an ideal metric to quantitatively
appraise power distribution at large radii.
In the process of defining the best or ‘target EF’ in which to be
used to measure IL, competing launch conditions were
considered. For example, an overly inflated EF at a particular
radius essentially underfills the fiber core and, although it may
provide highly repeatable results, this launch condition may
underestimate the IL and may not be able to discriminate the
quality of connectors with high enough resolution. Conversely,
if the EF at a particular radius is too low, the fiber core will be
overfilled and thus the IL will be overestimated due to increased
levels of DMA.
Furthermore, the repeatability of IL
measurements in this latter case will be compromised. Finally,
the tolerance limits on the ideal EF target should not be overly
burdensome to readily realize both in the factory and in the field.
Shown in Figure 3 is the measured IL of an optical link configured
identically to the link shown in Figure 2. The permanent link length
was 312 m long and constructed with OM3 fiber confirmed to
support error-free operation at 10 Gb/s data rates. A total of 66
different launch conditions, each of which was characterized by
CPR, was used for making IL measurements of the same optical
link. Although there is a strong qualitative relationship between
CPR and measured IL, there is not a good quantitative relationship,
as the 95 % confidence level in IL for a CPR of 22 is ± 0.39 dB.
From the data provided in Figure 3, it is readily seen that specifying
the launch conditions by CPR for making IL measurements may
result in large variations in measured channel IL.
The target EF, as well as the upper and lower limits on light
source and launch cord EF, have been determined through a
combination of comprehensive theoretical modeling and
experimental measurements executed in TIA TR-42.11.[10]
The EF target plus tolerance was selected to constrain the
measured loss variation to the larger value of ±10 % (in dB) or
0.08 dB. The EF target is defined for all the 4 combinations of
operating wavelength (850 and 1300 nm) and nominal fiber core
diameters (50 and 62.5 μm). The targets are only specified at 4
For legacy networking applications with data rates less than
10 Gb/s, this measurement uncertainty due to launch condition
variation was not of primary concern due to their large power
budgets. However, contemporary networking power budgets are
significantly more stringent and therefore the IL measurement
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radial points for 50 μm fiber and 5 radial points for 62.5 μm fiber.
An example EF template for MMF with a core diameter of 50 μm
and an 850 nm operating wavelength is provided in Figure 4.
1.0
0.9
0.8
0.7
EF
0.6
0.5
a)
a)
0.4
0.3
Figure 6. Near field images of the distal end of two different
launch cords excited by an 850 nm Light Emitting Diode
(LED): a) 3 m long patch cord with no mandrel wrap, and b)
a 3 m long patch cord with five wraps around a 25 mm
mandrel. Note the difference in intensity as a function of
radial position.
0.2
0.1
26
24
22
20
18
16
14
12
10
8
6
4
2
0.0
0
b)b)
Radius (μm)
Figure 4. EF template (shaded region) for MMF with a 50 μm
core diameter and an operating wavelength of 850 nm. Other
templates are defined for other core diameters (62.5 μm)
and/or operating wavelength (1300 nm). Although the shaded
region appears continuous, the EF target and tolerance limits
for 50 μm MMF are only quantified at 4 discrete radii denoted
by horizontal black bars: 10, 15, 20 and 22 μm .
Define three intensity summations (SI, Sr, Sc) in relation to T as
follows:
(2)
Magnification & Attenuation
Optics
CCD
Camera
LED
Image
Digitizer
Computer
The location of the image centroid, (X0, Y0) in units of pixel
number is found from
X0 = Sc / SI
Launch
Cord
Y0 = Sr / SI
The pixel numbers (i = 1, 2, …, Nrows and j = 1, 2, …, Ncols) can be
converted to equivalent absolute displacements (μm) with the near
field system magnification factors Sx and Sy which have units of
μm/pixel. The distance from the centroid to the image edges, DL,
DR, DB, DT, is given by
Figure 5. Schematic measurement setup for measuring
near field images.
4. Encircled Flux Measurement
Encircled flux is determined by analyzing the near field emission
pattern of the launch cord coupled to the light source.[11] The
near field image of the light source is simply a magnified
2-dimensional rectangular array of optical intensity measured by a
light detector array (i.e., CCD or CMOS camera). An example
near field imaging system is shown in Figure 5 and example
images are shown in Figure 6.
DL = Sx · X0
DR = Sx · (Ncols - X0)
DB = Sy · Y0
(4)
DT = Sy · (Nrows - Y0)
The nearest edge is given by
D = min(DL, DR, DB, DT)
Once the raw intensity array has been captured with a calibrated
near field imaging system, the 2-dimensional rectangular intensity
array must be converted to a 1-dimensional vector of average
intensity versus radial distance from the image centroid. This
information can then be used to calculate the EF.
For the rectangular image from the active elements of the imaging
array Imax, Imin is the maximum, minimum intensity in counts of
Ii,j, i = 1, 2, …, Nrows and j = 1, 2, …, Ncols. A threshold, T, is set
as
T = 0.1 (Imax – Imin)
(3)
The number of complete rings, centered on the centroid (NR) that
will fit within the area of the image is
NR = (D - W)/ W
(6)
where W is the ring width and a user defined input value (e.g.,
W = 0.2 μm). The distance from the (i, j) pixel to the centroid is
Ri,j, and given by
Ri , j = S y2 ⋅ (i − Y0 ) 2 + S x2 ⋅ ( j − X 0 ) 2
(1)
(7)
The ring index, ki,j, corresponding to Ri,j is given by
ki,j = trunc (Ri,j /W) + 1, ki,j = 1, 2, …, NR
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(8)
Proceedings of the 57th IWCS
cable had a length of 312 m and was connected to the fiber
cassettes via MPO connectors. The 12 channel SC simplex
cassettes also contained OM3 fiber. Three different launch cord
configurations were tested: launch cords with no mandrel wrap,
launch cords with two turns around a 25 mm mandrel and launch
cords with five turns around a 25 mm mandrel. To improve the
statistics, 2 launch cords from each of the three configurations was
tested. Additionally, 11 different 850 nm LEDs were used as the
light sources. Each of the 11 LEDs was connected to each of the
six launch cords. The receiving patch cord was also 3 m long. In
summary, a total of 66 unique samples were tested (11 LEDs x 2
launch cords x 3 configurations = 66).
where trunc(x) is x truncated to the next lower integer and NR is
the total number of rings. The average optical intensity, Iring, for
each ring and the average radius of each ring, Rring is determined
by taking the sums for adjacent and two overlapping rings as a
method to smooth the results.
There will be a collection of pixels that have the same ring index,
k, dropping the subscripts i and j in Equation (8) for clarity. Those
pixels will all be in the same ring of equal distance to the centroid
(to within W). The following sums are computed
S R (k ) =
NR
∑ R'i, j ;
k =0
S I (k ) =
NR
∑ I 'i, j ;
k =0
SC (k ) =
NR
∑ ni, j
k =0
(9)
The LEDs were surface emitting (SLEDs) and packaged in an ST
receptacle form factor which conveniently connected to the ST-toSC launch cords. It is expected that the Numerical Aperture (NA)
and Mode Field Diameter (MFD) of all 11 LEDs exceeded that of
the launch cords NA and MFD and therefore met the overfill
conditions. Furthermore, referring to Figure 3, each of the CPRs
met the overfilled Category 1 requirements (20 < CPR < 24 dB)
described in OFSTP-14A.[7] Each of the launch patch cords was
3 m long and fabricated with OM3 fiber.
where (R'i,j, I'i,j, ni,j) is the sum of all (Ri,j, Ii,j, number of i & j
indices) that have the same ring index, k. The mean radius,
Rring(k), and intensity, Iring(k), for each ring is given by
Rring(k) = SR(k)/SC(k)
Iring(k) = SI(k)/SC(k)
(10)
Encircled flux, EF(r), is given by
r
EF (r ) =
∫0
∞
∫0 r '⋅I ring (r ' ) ⋅ dr '
r '⋅I ring (r ' ) ⋅ dr '
Initially, the near field for each of the samples was recorded. The
LEDs were DC biased such that the nominal fiber coupled power
was –20 dBm. At this power level, no optical attenuation was
needed to prevent near field camera saturation. Each of the
images was averaged 256 times and the launch fiber was not
disturbed during the image acquisition. After image acquisition,
each of the raw binary images was processed with our internal EF
calculation algorithm which is compliant with FOTP-203.
(11)
This is a fraction of the total amount of optical power from the
centroid to a ring radius r divided by the total optical power.
5. Encircled Flux and IL Measurements
A series of IL measurements was taken on a fiber optic link
configured identically to that shown in Figure 2, with various
launch conditions. The 12 fiber 50 μm core diameter OM3 fiber
The average EF for each of the three launch cord preparations (22
EFs per each launch condition) is provided in.
Figure 7. Average EF versus radius for the 3
launch cord preparations measured: five wraps
around a 25 mm mandrel, two wraps around a
25 mm mandrel, and no wraps. a) shows the entire
radial scale while b) and c) show expanded radial
sections for improved clarity. The EF limits are
represented by horizontal black bars at discrete
radii.
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Qualitatively, the EF results shown in this figure are in
accordance with expectations: as the number of turns around the
mandrel increases, the greater the effect of mode filtering at high
radii which will result in the EF at a given radii to increase. With
respect to the upper and lower limits of the EF target, the launch
cords with five turns around a 25 mm mandrel are slightly
‘underfilled’, or above the EF target, at the 20 μm and 22 μm
control radii. Conversely, for those launch cords that were not
mandrel wrapped, there is only a limited amount of mode filtering
at high radii, resulting primarily from the fiber and cable itself,
and therefore a larger fraction of power propagates at larger
distances from the centroid. This reduces the EF at a given radius.
With respect to the EF limits, these launch conditions are
‘overfilled’ and below the EF target at the 20 μm and 22 μm
control radii.
18
Frequency
12
2 wraps
1.86
0.05
1.94
1.78
1.63
0.05
1.69
1.53
no wraps
2.50
0.11
2.33
2.01
10
8
6
4
2
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
1.5
0
Channel IL (dB)
Figure 9. Channel IL histograms for the three launch cord
preparations.
The effect of the DMA within the link is highlighted by the
differences in IL as measured by the different launch cords; the
full range of measured IL was 0.80 dB (2.33 dB – 1.53 dB).
Launch cords that did not utilize any mandrel wraps may
overestimate the IL of the channel due to the fact that reference
power measurements made with only the short 3 m launch patch
cord may not adequately remove the cladding modes launched
into the fiber by the LED. The power in these modes will most
probably be lost at the first few connections or in the first many
meters of the link. This type of power loss is largely insignificant
in 10 Gb/s applications that utilize VCSELs with underfilled
launch conditions.
1.00
0.98
0.96
0.94
EF
mean
SD
max
min
14
Figure 8 shows the measured EF for the launch cords that had two
wraps around a 25 mm mandrel. All 11 LEDs and both launch
cords, or a total of 22 samples, complied with the EF template at
each control radii. The standard deviations of EF at the 20 μm
and 22 μm control radii were determined to be 0.005 and 0.002,
respectively.
0.92
0.90
0.88
0.86
0.84
19.5
5 wraps
16
20.0
20.5
21.0
21.5
22.0
22.5
The IL results from the launch cords that were mandrel wrapped
showed improved agreement and small loss variations. As
expected, the launch condition with less mode filtering (i.e., two
mandrel wraps), and therefore a greater fraction of power in the
extremities of the fiber core, more conservatively quantifies the
channel IL. Although the average difference in channel IL is
small in this case (0.23 dB), this difference would become more
exaggerated as the quality of the channel decreases due to
increased levels of connector loss and DMA.
23.0
Radius (μ m)
Figure 8. Measured EF for the 22 samples (11 LEDs x 2
launch cords) that utilized two wraps around a 25 mm
mandrel.
After the near field images were acquired and the EF had been
calculated, the IL of the optical link was quantified with each of
the 66 samples.
The optical power meter used for the
measurements is currently traceable to the National Institute of
Standards and Technology (NIST). A histogram of the IL
measurements is provided in Figure 9.
The loss variation for the IL measurements taken with launch
cords with 2 mandrel wraps was ± 4.3 % and the loss variation for
the launch cords with 5 mandrel wraps was +3.7 % and –6.1 %,
both of which meet the ± 10 % loss variation objective of the EF
target loss. Also, the standard deviation of these two launch cord
preparations was 0.05 dB. The EF measured at 22 μm versus
channel IL is provided in Figure 10.
Several important conclusions can be made from this data. First
however, it is important to note the channel IL measured by each
of the launch cord preparations is relatively small considering the
link consisted of four mated pairs of connectors (two SC-to-SC
connections and two MPO-to-MPO connections inside the fiber
cassettes). Attenuation due to the fiber cable alone was measured
to be 0.72 dB. Consequently, all of the connectors in the link are
high quality.
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connectors in each of the other 9 patch cords (see Figure 11).
Method 1 is intended to be part of a qualification process for
fiber optic component suppliers. The total number of IL
measurements with this method is 360 (9 test PCs x 2
connectors per PC x 10 launch PCs x 2 connectors per PC =
360).
1.00
underfilled region
0.99
2 wraps
EF at 22 μ m
0.98
upper EF limit
5 wraps
0.97
Method 2. 15 patch cords and 5 adapters are selected at
random. 5 of the 15 patch cords are randomly selected as the
test interface, or launch patch cord (see Figure 11). The
remaining 10 patch cords are tested against these launch patch
cords. Method 2 is intended to be part of a process control
once approval of Method 1 has been attained. The total
number of IL measurements with this method is 100: (10 test
PCs x 2 connectors per PC x 5 launch PCs x 1 connector per
PC = 100).
lower EF limit
0.96
no wraps
0.95
0.94
overfilled region
2.4
2.3
2.2
Channel IL (dB)
2.1
2.0
1.9
1.8
1.7
1.6
1.5
0.93
Figure 10. Measured EF at 22 μm versus measured channel
IL for the 3 launch cord preparations measured: five wraps
around a 25 mm mandrel, two wraps around a 25 mm
mandrel, and no wraps.
Connector 1B
LED
Connector 1A
a)
6. Random Mating
The most widely accepted method of measuring the IL of MMF
optic connectors utilizes a nearly ideal or reference patch cord as
the test interface to quantify the performance of every individual
connector. In this method a single well-controlled, nearly ideal,
or ‘reference’, patch cord is used as the test interface for each
connector measured. The connector and fiber that comprise the
reference patch cord have tighter geometrical tolerances than
standard patch cords. Since each connector is measured using this
nearly ideal patch cord, there is a high degree of measurement
repeatability not only internally, but also across fiber optic
component suppliers, test equipment suppliers and end users.
This approach has proven to be cost effective and it produces
accurate and repeatable results.
Connector 2A
LED
Patch Cord
Under Test
Mode
Filter
Power Meter
Connector 2B
b)
Figure 11. Schematic measurement setup for making IL
measurements according to the random mating and reference
patch cord methods.
Another method, preferred in some market segments, to measure
the IL of MMF optic connectors is the random mating method
according to standard IEC 61300-3-34.[9] In this method,
randomly selected patch cords, instead of those with tight
tolerances, are used as the test interface to measure the IL for each
of the sampled connectors under test. Ideally, this method
quantifies the IL of an entire population of connectors based upon
sampled IL measurements of randomly selected connectors. The
average, standard deviation, and maximum IL, from these sample
measurements are used to describe an entire population of
connectors. It is important therefore, to ensure that that the
randomly selected samples are representative of the entire
population; a subset of the population will skew the results. Most
importantly, every connector in the population may not be tested.
The patch cords and adapters used with this procedure must also
be selected at random from the total population for it to be
accurately characterized.
In order to appraise the quantitative difference between the
reference patch cord and random mating IL measurement methods
for a specific representative patch cord type, a group of patch
cords were ordered directly from commercially available stock
and chosen to be tested per the different methods. The randomly
selected patch cords were PANDUIT Opti-Core® 10Gig™
50/125 μm (OM3) LC-to-LC simplex, 1.6 mm jacket, 15 m long
patch cords. The light source used for the measurements was a
LED with a nominal center wavelength of 850 nm. The launch
cords employed 25 mm mode filters in order to ensure that launch
conditions would be similar to those used for reference patch cord
measurements. To consider only the optical losses associated
with the connectors, an experimentally determined fiber
attenuation factor was uniformly subtracted from each of the
measurement results.
Two test methods are specified in the random mating standard:
The histograms of the IL measurements are provided in Figure 12.
Since the required number of measurements for the two methods
is different, the relative % frequency is plotted. Again, it is
important to note the measured connector IL values measured by
both reference patch cords and random mating methods is
exceedingly small (average = 0.06 dB). Consequently, all of the
Method 1. 10 patch cords and 10 adapters from the
population to be characterized are selected at random. A
labeling and measurement sequence is defined such that each
connector in each patch cord is used as the test interface, or
launch patch cord, for measuring the IL of each of the
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connectors measured in this study are of very high quality and it is
expected that the difference in IL measured with reference patch
cord and random mating methods will diminish. Lower quality
connectors with higher loss will exaggerate this difference.
Furthermore, even higher grade reference patch cords, or research
grade reference patch cords, which exhibit nearly undetectable IL
when mated with one another, may also exaggerate the difference
between the average IL measured with a research grade reference
patch cord and randomly selected patch cords.
7. Conclusions
Insertion loss is a critical parameter for reliable, high performance
optical networks operating at 10 Gb/s and beyond. Accurate
knowledge of the IL of each connector, patch cord, and cassette
within the optical link ensures that network designers and
installers can design and deploy the most effective solution. Most
fiber optic component suppliers and end users employ reference
patch cords and coupled power ratio to specify the launch
conditions for performing IL measurements. Although coupled
power ratio specifications do reduce the measured IL variance
somewhat, by its very definition, coupled power ratio is ill suited
to specifying the modal power distribution at the extremities of
the fiber core which must be done for highly repeatable IL
measurements.
40
35
Method
Ref PCs
1
2
Frequency (%)
30
25
Mean
dB
0.06
0.06
0.06
SD
dB
0.05
0.06
0.05
n
140
400
100
Alternatively, encircled flux, which is determined by analyzing
the near field emission pattern, has been shown to be capable of
quantifying the power distribution at large radii. Furthermore,
those light source and launch cord combinations that meet a series
of encircled flux specifications or limits, have been
experimentally confirmed to enable highly relevant and repeatable
IL measurements.
20
15
10
5
An alternative IL measurement method, called random mating,
can be used to characterize the IL of a large population of
components via random sampling. In practice this method cannot
provide either the performance data at the single component level
required for reliable network deployment and operation nor a
uniform sampling methodology required for comparing competing
vendor performance specifications.
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0
Measured IL (dB)
Figure 12. Histograms of the IL measurements made
according to the reference patch cord and random mating
standards.
8. Acknowledgements
Although the random mating measurement method is intended to
provide a realistic estimate of the expected average IL for
connectors utilized within the field, several factors prevent it from
being the preferred IL metric for routinely appraising and
comparing the performance of connectors. The most important
factor is that results from a random mating measurement are valid
only for the populations of connectors tested. In order for the
random mating statistics to be applicable to a larger population
than tested, every possible component and manufacturing process
variable must be represented by the population from which the
random samples are selected. Identifying all component and
process variables for highly sensitive and advanced components
like fiber optic connectors is impractical and therefore the
connectors tested may not accurately represent every possible
connector in the population.
The authors would like to acknowledge sample testing and
preparation assistance provided by Philip Kay and Eddie Hight.
9. References
[1] http://www.ieee802.org/3/ae/public/adhoc/serial_pmd/
documents /10GEPBud3_1_16a.xls
[2] Pimpinella, R. & Brunsting, A., "Differential Mode Delay
(DMD) for Multimode Fiber Types and Its Relationship to
Measured Performance", Proc. OFC/NFOEC, 2005.
[3] Pimpinella, R., Lane, B. & Brunsting, A., "Correlation of
BER Performance to EMBc and DMD Measurements for
Laser Optimized Multimode Fiber”, Proc. 56th IWCS, 2007.
[4] TIA/EIA-568-B.3 "Optical Fiber Cabling Components
Standard", 2000.
Moreover, due to the large number of measurements required to
execute the random mating test method, it is only practically and
economically applied in a sampling scheme, which cannot provide
end users individual component level performance verification.
Furthermore, since individual sampling plans are not specified in
the random mating standard, this test is not likely to be
implemented by component suppliers in an identical manner and
therefore is not the most practical metric for comparing different
vendors’ components. For example, it may be difficult for a
customer to determine if one vendor has selected ‘random’
samples from a specially tuned manufacturing run and another
competing vendor selected ‘random’ samples pulled directly from
stock. These populations would likely yield different IL statistics.
International Wire & Cable Symposium
[5] ISO/IEC 11801 “Information technology – Generic cabling
for customer premises”, 2002.
[6] TIA/EIA-455-171A "FOTP-171 / Attenuation by
Substitution Measurement for Short-Length Multimode
Graded-Index and Single Mode Optical Fiber Cable
Assemblies", 2001.
[7] TIA/EIA-526-14A "Optical Power Loss Measurements of
Installed Multimode Fiber Cable Plant", 1998.
[8] IEC 61280-4-1 “Fibre-optic communication subsystem test
procedures - Part 4-1: Cable plant and links - Multimode
fibre-optic cable plant attenuation measurement”, 2004.
[9] IEC 61300-3-34 "Fibre-optic interconnection devices and
passive components – Basic test and measurement
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procedures: Part 3-34 Examinations and measurements –
Attenuation of random mated connectors", 2001.
Applied Optics, which regularly publishes reviews in that journal.
He has also served as President of the Chicago Chapter of SPIE
and as a Session Chairman of NFOEC 2006. Al has nine years
experience in development of fiber optic products, including
variable attenuators (1 patent), multi-fiber ferrules, dense
wavelength division multiplexers, multimode power budgets
(IEEE 2004 paper) and mathematical simulations.
[10] TIA TSB-178 "Launch Conditions Guidelines for Measuring
Attenuation of Installed Multimode Cabling", 2008.
[11] TIA/EIA-455-203 "Launched Power Distribution
Measurement Procedure for Graded-Index Multimode Fiber
Transmitters", 2001.
Before that he developed and contributed to the following:
sensitive fluorescence instrumentation for bio-assays, optical
readhead for a blood glucose analyzer (1 patent) which sold 1.5
million instruments worldwide, unique and user-friendly
calibration method for that glucose analyzer, and optical
components for flow cytometers. He was recognized with the #1
worldwide award conferred by Bayer Corporation for
distinguished technical achievement.
Biography of Authors
Brett Lane, Ph.D.
Rick Pimpinella, Ph.D.
Dr. Brett Lane is a Research Engineer in the Fiber Research
Department of Panduit Labs, Panduit Corp. Brett has more than
10 years of experience in fiber optics and optoelectronic devices
and currently has active research projects focused on differential
mode delay, bit-error rates, plastic optical fiber, and highperformance fiber optic connectors. Prior to joining Panduit in
2003, he worked at Molex Fiber Optics on advanced transceiver
design. Brett is the author or co-author of over 25 technical
publications on fiber optic, electronic and optoelectronic
communication devices. He holds 2 US patents in this field. Dr.
Lane received his Ph.D. in Electrical Engineering from
Northwestern University in 2001 and B.S. in Mechanical
Engineering from the University of Texas at Austin in 1996.
Dr. Rick Pimpinella is the Fiber Research Manager at Panduit
Laboratories, Panduit Corp. He has more than 26 years of
experience in applied research and the development of fiber optic
components and sub-systems. Before coming to Panduit, Dr.
Pimpinella was a Technical Manager at Bell Labs, where he was
responsible for the design and development of Fiber Apparatus
and Remote Fiber Test Systems. During his 20-year tenure at Bell
Labs, Dr. Pimpinella was a Member of Technical Staff and in
1994, was appointed Distinguished Member of Technical Staff.
He remains active in his studies of the fundamental aspects of
multimode fiber transmission and the intrinsic properties of modal
propagation.
Al Brunsting, Ph.D.
Dr. Pimpinella serves as a member of the IEEE 802.3 optical fiber
standards bodies. He is the author or co-author of 22 technical
papers as well as other articles on aspects of fiber optics and
multimode fiber performance. He holds 45 US patents on optical
components, subsystems, intelligent test and monitoring systems
and other devices.
Dr. Pimpinella received his Ph.D.
(Experimental Solid State Physics, 1982), M.S. (Theoretical
Physics, 1978) and B.S. (Physics, 1976) degrees from the
Polytechnic Institute of New York.
Dr. Al Brunsting, is a Principal Engineer in the Fiber Research
Department of Panduit Labs, Panduit Corp. He has 14 issued
patents and over 18 publications in the refereed technical
literature. He served as chairman of the Patents Review Panel for
International Wire & Cable Symposium
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Proceedings of the 57th IWCS