NAT'L INST. OF STAND & TECH

II NivST

PUBLJCATIONS

NIST Measurement Services:

Optical Fiber Power Meter nist

Calibrations at NIST ^^^^

250-54

Igor Vayshenker

Xiaoyu Li

David J. Livigni

Thomas R. Scott

Christopher L. Cromer

X

100

.057

NO.250-54

2000

NIST CENTENNIALS

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NIST Special Publication 250-54

NIST MEASUREMENT SERVICES:

Optical Fiber Power Meter Calibrations at NIST

Igor Vayshenker

Xiaoyu Li David J. Livigni

Thomas R. Scott

Christopher L. Cromer

Optoelectronics Division

Electronics and Electrical Engineering Laboratory

June 2000

U.S. Department of Commerce

William M. Daley, Secretary

Technology Administration

Dr. Cheryl L. Shavers, Under Secretary of Commerce for Technology

National Institute of Standards and Technology

Raymond G. Kammer Director
Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply

recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended

to imply that the entities, materials, or equipment are necessarily the best available for the purpose.

National Institute of Standards and Technology Special Publication 250-54

Natl. Inst. Stand. Technol. Spec. Publ. 250-54, 41 pages (June 2000)

CODEN: NSPUE2

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 2000

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402-9325
Contents

1. Introduction 1

2. Laboratory Standard 2

3 . Optical Fiber Power Meter Calibrations 6

3 . 1 Measurement Equation 6

3.2 Calibrations Using Fixed Laser Wavelengths 6

3.2.1 Measurement Assurance Program 1

0

3.3 Calibrations Using Variable Wavelengths From Tunable Laser Diodes 11

3.3.1 Tunable Laser Diode 11

3.3.2 Measurement System 13

3.4 Fiber Connector Issues 14

4. Uncertainty Assessment 15

5. Future Work 22

6. References 22

Appendix A. Laser Diode Optical Spectra 24

Appendix B. Measurement Flow Chart 25

Appendix C. Sample of a Calibration Report 26

Appendix D. Wavelength History 32

Appendix E. Sample Results and Shipping Instructions for MAP 33

Appendix F. Sample Data Sheet for MAP 34

Appendix G. ECPR Linearity Measurements 35

Appendix H. ECPR Uniformity Scans 36

iii

Optical Fiber Power Meter Calibrations at NIST

Igor Vayshenker, Xiaoyu Li, David J. Livigni, Thomas R. Scott, and Christopher L. Cromer

National Institute of Standards and Technology

325 Broadway, Boulder, CO 80303, USA

NIST has established measurement services for the calibration of optical fiber power

meters at the three nominal wavelengths of 850, 1300, and 1550 nm using either

coUimated beam or optical fiber/connector configurations. This paper describes the

measurement standards, techniques, systems, and uncertainties involved with the

NIST optical fiber power meter calibration services.

Key words: calibration; cryogenic radiometer; measurement service; optical power;

optical fiber power meter; spectral responsivity; tunable laser diode; uncertainty;

uniformity.

1. Introduction

The optical fiber power meter (OFPM) is perhaps the most common type of test equipment used

to support the development and implementation of optical fiber systems. To address the inherent

metrology requirements, NIST has developed and implemented measurement services to help

characterize these instruments [1]. These measurement services consist primarily of absolute laser

power calibrations using either coUimated beam or optical fiber/connector configurations. In

addition, NIST provides measurements of uniformity, nonlinearity, spectral responsivity (based

both on tunable lasers and broadband incoherent light sources) for OFPMs. Calibrations are

available at the three principal wavelength regions used by the optical fiber telecommunications

industry, 850, 1300, and 1550 nm and, consequently, our measurement services are based

primarily on these wavelengths. Other optical power meter users (e.g., compact-disc player

manufacturers, users of erbium-doped fiber amplifiers) are additionally interested in wavelengths ^ of 670, 780, and 980 nm. We have also incorporated these wavelengths into our absolute laser

power calibration program.

Most OFPMs are based on photodiode sensors made of either silicon (Si), germanium (Ge), or indium gallium arsenide (InGaAs) and, thus, the accurate calibration of these devices must

accommodate the inherent characteristics of these devices (e.g., output sensitivity to both spectral

and spatial profile of the incident electromagnetic radiation). The electromagnetic radiation is typically provided by laser diodes operating in single-mode or multimode configurations. Unlike

solid-state or gas lasers, which operate at well defined wavelengths, diode lasers (due to the

manufacturing process) do not operate at a specific wavelength (or center wavelength, for

muhimode lasers) but typically emit radiation that is within ±10 nm of some desired value.

Factors such as temperature variation can also change the wavelength profile. Consequently,

1
detectors which are spectrally sensitive can produce different outputs when exposed to equal

powers from different diode lasers or even the same laser under different operational conditions.

Naturally, for measurements of high accuracy, both the spectral responsivity of the detector and

the spectral pattern of the radiation emitted by the laser diode should be measured.

As shown in NIST studies [2-4], OFPMs can exhibit significant errors when measuring absolute

power of radiation delivered through connected fibers. This effect is predominantly due to the

reflection of radiation from the diode/window surface back onto the fiber/connector assembly and

then reflected back onto the detector. This reflected energy causes the optical power meter to

read higher than it would for a coUimated beam equal in power. The magnitude of this effect is a

function of both wavelength and connector type, and, as a result, the optical power meter should

be calibrated with the same fiber and connector with which it is to be used.

NIST optical-power measurement traceability is to the Laser Optimized Cryogenic Radiometer

(LOCR) [5-8] based on the electrical substitution method. The laboratory standard is an

electrically calibrated pyroelectric radiometer (ECPR) which is then used for the OFPM

calibration services. The ECPR has a thermal detector which has a black, highly absorbent

coating and has, accordingly, an output that is spectrally insensitive over the wavelength regions

of interest for OFPM calibrations. The low-reflectance surface of the ECPR allows it to be used

for both coUimated beam and optical fiber/connector measurements. The ECPR is used with a measurement system composed of laser diodes, fibers, connectors, fiber splitters, monitors, and

lenses to calibrate OFPMs. This measurement system can accommodate most commonly used

connector and fiber types.

The following sections of this paper will provide more detailed discussions of the measurement

systems presently used in the OFPM calibrations at NIST. Some aspects of these measurement

systems and measurement techniques are continually being improved and/or modified to

accommodate changing measurement requirements, e.g., adding different laser diodes, improving

the transfer standards and calibration software, etc.

2. Laboratory Standard

In this section we describe the laboratory standard which is used for OFPM calibrations. The

laboratory standard for the NIST optical fiber power measurements is a commercially available,

electrically calibrated pyroelectric radiometer which is calibrated optically against the LOCR. The

ECPR pyroelectric sensor is made of lithium tantalate that is covered with a gold-black coating on

one side. The gold-black coating (approximately 1 |im thick) has been evaporated and then

deposited under specific temperature and pressure conditions onto the lithium tantalate surface

[9]. When deposited in this manner, the gold forms small, interwoven strands which act to trap

incident light and, thus, make the gold surface appear black. Gold black is approximately 99 %

absorbent [1 0] in the visible and near-infrared regions.

2
Pyroelectric sensors produce an electrical voltage proportional to instantaneous temperature

changes [9] and, as a result, the laser energy incident onto the detector must be modulated in order to use this type of detector to measure CW radiation. The particular detector we use has a chopper wheel which is placed in front of the pyroelectric sensor and is used to 'chop' the beam

into pulses at a rate of 1 5 Hz. Because pyroelectric materials are also piezoelectric, vibration sources must be minimized.

The ECPR is frequently used as a laboratory standard in many optical fiber power calibration

laboratories because (1) it is sensitive to low power radiation, (2) it is relatively spectrally flat, and

(3) it has a low surface reflectance in the 600 nm to 1600 nm wavelength region. This particular

type of ECPR is used in the 10 to 1000 ^iW power range which is the range of primary

importance in optical fiber power calibrations. Below 10 ^iW the output becomes too noisy to use reliably and above 1000 |xW it becomes nonlinear. On the negative side, the ECPR has some

disadvantages: (1) nonuniformity of response across the detector surface and (2) fragile nature of

the sensor and gold-black coating.

Before the ECPR is used as a laboratory standard, it is first calibrated against the LOCR (direct

substitution) at wavelengths of 633, 1319, and 1550 nm using the system shown in Figure 1. Both

the LOCR and ECPR are placed on a motion-controlled stage. Various filters are used to 'clean'

the laser beam by removing high-order components. Power is stabilized to achieve high-accuracy

measurements. An optical chopper is placed in the beam when using the ECPR; the chopper is removed when using the LOCR. The LOCR was designed to accurately measure the

electromagnetic radiation produced by CW (continuous wave) laser sources in the milliwatt

power range. The LOCR was constructed to accommodate the unique characteristics of laser

radiation (e.g., nonuniform intensity profiles, temporal and spatial coherence) and can be used

over a wide wavelength range. The LOCR's standard uncertainty is 0.02 % at a power of 1 mW.

The results of several calibrations are given in Table 1 . The details of the ECPR calibration

against the LOCR are described in a separate document [11]. To verify the ECPR spectral

flatness, we calibrate it at several laser wavelengths against the national primary standard, the

LOCR.

The ECPR has an analog voltage output port, but due to the limited resolution of the digital-toanalog converter, this output lacks the accuracy of both the display and the BCD outputs;

consequently, to obtain the best ECPR measurement results, either the display reading or the

BCD output can be used. For the NIST ECPR calibration, the BCD output is used and is sent to a BCD-to-analog voltage converter. The analog voUage from the converter is then measured

with a digital voltmeter.

3
Figure 1 . Measurement configuration for ECPR calibration.

Table 1. Calibration factors for ECPR#618 referenced to LOCR.

Date Source wavel.

(nm)

Calibration

factor

Standard combined

uncertainty/%

11/98 633 0.9978 0.16

11/98 1319 0.9945 0.16

11/98 1550 0.9946 0.16

One of the major error sources for the ECPR is the variation of response of the detector for

radiation (at constant power) striking different spots of the detector surface. Figure 2 shows a contour map, generated fi"om a spatial uniformity scan that is performed on a NIST ECPR using a beam 2.0 mm (±0. 1 mm) in diameter (at 1/e^ intensity points) at a wavelength of 1557 nm and

using 0.2 mm beam steps. This scan was accomplished using a uniformity measurement system,

designed and developed at NIST for characterizing spatial response of optical detectors [12].

4
Relative responsivity (%)

-2.00 -1.00 0.00 1.00 2.00

X—Axis Position (mm)

Figure 2. Contour map of the entire dataset, 0.1 % contour line spacing.

The uncertainty due to the nonuniformity of the ECPR sensor can be minimized by always using

approximately the same size beam for both the LOCK measurements and for the optical power

meter calibration measurements. Also, the laser beam is always centered on the sensor surface

and the chopper wheel aperture. To assure that a beam of a similar size (during coUimated beam

measurements) is always used, we employ a laser beam-profile instrument to measure beam size at the detector location.

The quality-assurance procedure for checking the ECPR before a routine calibration is described

in Section 3.2.

5
3. Optical Fiber Power Meter Calibrations

In this section we describe the measurement equation and the OFPM measurement. We also

discuss Measurement Assurance Program (MAP) comparisons of OFPMs.

3.1 Measurement Equation

Upon completion of the OFPM calibration, the customer is given a calibration report that lists the

resulting calibration factor(s). The calibration factor is obtained by dividing device under test (DUT) net display reading by the incident power. Thus, if the display readings of the DUT are divided by the calibration factor, then, on the average, the resulting values will agree with the

NIST national standards. The calibration factor, is given below:

Fc=(Pdut*V,)/(Ps*V^, (1)

where Pd^ is the test power meter reading in units of optical power (nW), voltage or current,

Ps is the ECPR reading in units of nW,

V, is the monitor reading in units of V with the ECPR in place,

V2 is the monitor reading in units of V with the DUT in place.

Each of the variables in the eq (1) represents a signal with a background reading subtracted. The

calibration factor in this paper is the inverse of the correction factor described in reference [13].

Also, the correction factor obtained from our nonlinearity measurements [14] is used to 'correct' a calibration factor determined at a power of 100 |iW.

3.2 Calibrations Using Fixed Laser Wavelengths

Figure 3 shows the measurement system configuration used for coUimated beam and optical

fiber/connector measurements during the calibration of OFPMs. The ECPR is used for these

calibrations. The system contains several laser source plates, a connector converter stage (for

connectorized measurements), lens assembly (for collimated beam measurements), and a

positioning stage for comparing the ECPR and the test meter being calibrated.

An enlarged view of a laser source plate is shown in Figure 4. All system optical fibers are singlemode, whereas the customer's fiber may be either single-mode or multimode. Each laser source

plate contains a laser diode whose output is transmitted through a fiber to a fiber splitter from

which about 1 % of the energy travels through a fiber to a monitor detector. The remaining 99 %

of the energy is transmitted through another fiber to the meter being calibrated. Loose fibers

throughout the system are wrapped on spools 5 cm in diameter to minimize transient microbend

6
losses. Also, in this regard, all fibers are securely fixed so that they cannot move during the

measurements. All the lasers (except for 1550 nm) are of Fabry-Perot types and have several

longitudinal (spectral) modes (see Appendix A). The coherence length of each of these lasers is approximately a few centimeters. The 1550 nm laser is a distributed feedback (DFB) laser with a coherence length of a few hundred meters. The lasers' wavelengths are checked periodically

(twice a year). Some of the lasers have been used for over 10 years and have demonstrated high

stability over that period.

Digital

Voltmeter

Temperature

Controller

Laser Powei

Siq)ply

Sample

(}St

Rotatable Mounting

Platform

850 nm

KPlate

Positioning

Rail

Data Acquisiti(H} &

Analysis System

1550 nm

Plate NISTECPR

chopper

User's fiber/connector or collimated beam

BCD/GPB

Converter

I NIST Standard (ECPR)

User Test Meter

Figure 3. Measurement system.

7
Fibato

connector

converter

plate

Figure 4. Laser source plate.

As shown in Figure 4 (as well as in Figure 3) a U-shaped collimator fixture is positioned in the

propagation path following each diode laser. This fixture contains two lenses that provide a coUimated beam for the ECPR chopper wheel to access. When the chopper wheel is inserted into

the space provided by this fixture, a chopped beam is then incident on the detectors (i.e., the

monitor and the ECPR). The same chopper is used when the ECPR is calibrated against the

LOCR. A 'sample-and-hold' current-to-voltage converter is used to monitor the output, and

provide an equivalency between powers in CW and chopped beams (the difference between CW

and chopped signals contributes to the uncertainty of a measurement). This converter utilizes a

capacitor that stores the peak voltage reading fi-om the chopped signal until the digital voltmeter

takes a reading. Each time the ECPR is used for measurements in this system, the chopper wheel

is inserted into the collimator fixture opening and is removed when not using the ECPR. The

misalignment of the chopper is included in the uncertainty calculation.

For collimated beam measurements, a lens at the end of the fiber path provides a collimated beam

to the ECPR and test meter. Note: when using the collimated beam, the calibration factor may

vary if the power meter under test has nonuniform spatial responsivity and/or a window that

exhibits transmittance variations fi^om coherent interference of multiple reflections. These effects

may increase the measurement variation that depends on specific properties of the meter under

test. For connectorized measurements, the customer's fiber is connected to the measurement

system, which accepts a popular FC/PC (physical contact) optical fiber connector. If the

customer's fiber connector is different fi^om FC/PC type, we use a hybrid jumper cable.

8
The first step in a calibration measurement is the determination of power in either the coUimated

beam or fi^om the end of a fiber, whichever is appropriate for a particular situation. For this

measurement, either the ECPR is placed in the path of the collimated beam or else the customer's

fiber is connected to the ECPR using appropriate adapters. In either case, both the ECPR

readings and the monitor detector vohages, V, in eq (1) are recorded. Twenty pairs of

measurements are taken over 30 s (we wait 30 s before taking the measurements for the ECPR

readings to stabilize). Then the ECPR is moved and replaced by the test meter. For

connectorized fiber measurements, the fiber connector is moved fi^om the ECPR to the test meter.

The test meter readings and the monitor detector voltages, in eq (1) are then recorded. Ten or twenty pairs of measurements are taken. Finally, the ECPR is placed back into the beam path (or

reconnected to the fiber), and, again, the ECPR and monitor detector readings are recorded.

Twenty pairs of measurements are taken. The flow chart of the measurement is shown in Appendix B. The absolute power incident onto the test meter is established by the average ECPR

power readings. Power changes (e.g., due to diode laser instability) are taken into account by the

monitor detector readings. Thus, this method relies on the short-term stability of the power

splitting between the monitor and a customer's fiber, not on its actual value. The 'before' and

'after' ECPR/monitor detector measurements help confirm the stability of power splitting. If the

ratio change exceeds a threshold of 0.25 %, then the measurements are repeated since it indicates

something in the system has not stabilized. This difference is used to calculate the uncertainty of

the calibrations. To check the performance of the sample-and-hold circuit and the stability of the

laser sources, two measurements are taken, with and without the chopper. If the difference of

these two signals exceeds a threshold of 0.25 %, then the operator will redo the measurements.

This difference is found for a quality-control check only and is not used for the uncertainty

calculations. Usually, six runs are performed on a test meter; for quality control two sets of three runs are performed on different days.

We provide quality assurance for the laboratory standard by using a check standard. Before each

routine calibration, the check standard (a dedicated power meter, e.g., HP 8152A with a Ge

sensor 8 152 IB #155) is placed in the measurement system shown in Figure 3. The calibration is performed with a dedicated fiber and the results are stored in a history file. The calibration factor

of each particular run is compared with the value obtained in the past. Table 2 shows the results

of measurements performed on the NIST check standard.

A sample copy of a calibration report is provided in Appendix C.

9
Table 2. Calibration factors for check standard at 1307 nm.

Date Calibration factor

(reading/^iW)

06-12-1998 1.002

06-15-1998 1.001

07-01-1998 1.000

08-18-1998 1.002

08-19-1998 1.000

08-25-1998 1.001

09-23-1998 1.001

10-05-1998 1.000

12-08-1998 1.002

01-05-1999 1.003

Average 1.001

St. dev. (%) 0.09

Because of spectral-sensitivity issues regarding diode detectors, we must know the center

wavelengths of the laser sources for the measurement system. Since the values of center

wavelengths have been historically very stable, we periodically (usually twice a year) measure them using a commercial Optical Spectrum Analyzer (OSA). Before the measurements begin, the

OSA is warmed up for at least an hour and is calibrated using He-Ne gas lasers that emit radiation

at well-defined wavelengths in the 633 nm and 1523 nm regions. The history file of the

measurements can be found in Appendix D.

3.2.1 Measurement Assurance Program

NIST maintains a set of calibrated transfer standards which are available for Measurement

Assurance Program (MAP) comparisons of OFPMs. These transfer standards are calibrated using

the OFPM calibration system discussed in section 3.2. First, NIST calibrates an appropriate

transfer standard using the MAP participant's fiber cable (if applicable), then the meter and the

fiber cable are sent to the MAP participant, who compares the NIST transfer standard to his/her

laboratory standard. Shipping instructions are included with the meter (see Appendix E). The

participant fills out a sample data sheet with his/her measurements, and sends the meter back to

10
NIST with the data sheet (see Appendix F). The results of the two sets of NIST measurements

are averaged. Then, participant's resuhs are compared to the NIST average. If the difference

between two sets of data is larger than the uncertainty of the measurement (approximately 0 .5 %),

the measurements are repeated. The MAP Calibration Report then summarizes the results of this

comparison including an assessment of the associated uncertainties.

3.3 Calibrations Using Variable Wavelengths from Tunable Laser Diodes

NIST provides services for OFPM calibrations at fixed wavelengths using both coUimated beam

and fiber/connector configurations. However, most users have laser sources whose center

wavelengths differ fi-om those used by NIST. To apply NIST's calibration results to the test meter, the meter user must know both the spectral responsivity of the detector and the source

wavelength. If the user's source wavelength is different fi"om the wavelength used by NIST

during the calibration, the calibration results must be adjusted appropriately. Therefore, it is important to either calibrate the OFPM at the user's laser source wavelength, or provide the user with a spectral responsivity information for the detector used in the OFPM [15].

In this section, we describe a measurement system developed by NIST to calibrate OFPMs at adjustable wavelengths using either coUimated-beam or connectorized-fiber configurations. This

calibration system uses power-stabilized tunable laser diodes which operate in the three fiber

optics windows of 850 (±15) nm, 1300 (±30) nm, and 1550 (±30) nm. The lasers include optical

isolators to decrease feed back reflections and improve stability (see Figure 5). This system is similar to the system described in Section 3.1.

3.3.1 Tunable Laser Diode

To minimize potential measurement errors associated with source wavelength and detector

spectral responsivity, we have installed tunable laser sources in the measurement system. The

gain medium of the tunable laser is a conventional laser diode but the internal Fabry-Perot

resonator is disabled by an antireflection coating on one of the facets. An external cavity is created by adding an external diffraction grating that acts both as a mirror and a wavelengthselective element.

The output power, single-mode operation, and wavelength stability depend strongly on

temperature stability. CoUimating lenses, shown in Figure 5, collect the divergent laser beam.

Since the beam diverges as much as 45°, the lenses must have a numerical aperture (NA) of 0.4

and have surfaces whose wavefi^ont aberrations are less than A/4, where X is the wavelength ofthe

laser radiation.

The lasers use optical isolators to decrease backreflections, which deteriorate the laser power

stability. We have also added a radio-fi^equency source (10 ^W in power and 10 MHz in

fi-equency) to the DC drive current to decrease source coherence and further reduce effects of

backreflection.

11
Laser Cavity

Figure 5. Diagram of tunable laser with an external cavity.

Figure 6 depicts the optical spectra of our 1300 nm tunable laser diode at three selected settings.

The two extreme spectrum lines correspond to two extreme wavelengths that the laser is capable

of producing.

100

OL^ 60 • O

Q.^ 40 3

UJ

CC 20

0 \ <——I M 1——'

1 1260 1280 1300 1320 1340 WAVELENGTH (nm)

Figure 6. Spectra of 1300 nm tunable laser diode at three different grating settings.

12
Monitor

Collimator Figure 7. Tunable laser diode stage.

3.3.2 Measurement System

Since this system is similar to the measurement system that uses fixed-wavelength laser diodes, we

will not describe this system in detail (see Section 3.1 and Figure 3). An enlarged view of a laser source plate is shown in Figure 7. All the optical fibers in the system are single-mode. Each plate

contains a laser diode whose output is transmitted to a fiber splitter fi-om which about 5 % of the

power is diverted to a monitor and about 1 % of the power to the calibrated OSA.

The remaining power is transmitted through a fiber to the meter being calibrated. All fibers are securely fixed so that they will not move during the measurements. A U-shaped collimator is positioned in the propagation path following each diode laser. This collimator contains two

lenses, which provide a coUimated beam for the ECPR chopper wheel. When the chopper wheel

is inserted into the space provided by this fixture, a chopped beam is then incident onto the

detectors (the monitor and the ECPR). To illustrate its capabilities. Figure 8 depicts measured

responsivity of a typical germanium detector in the 1550 nm region using the NIST tunable laser

system.

13
1

0.95

0.9 ^ 0.85 w

I

0.8

Q.W

y 0.75

0.7

0.65

1520 1530 1540 1550 1560 1570 WAVELENGTH (nm)

Figure 8. Sample Ge detector responsivity curve using 1550 nm tunable laser diode.

3.4 Fiber Connector Issues

In several optical fiber connector studies [2-4], we showed that the OFPM responsivity can vary

dramatically when using various types of connectors or even connectors of the same type but

from different vendors. We investigated the magnitude of this connector-induced variation by

calibrating several types of OFPMs at wavelengths of 850, 1310, and 1550 nm. In these

measurements we varied the connector type and connector vendor, and observed the resulting

offsets in calibration results.

When optical fiber power is measured, radiation is transmitted to an OFPM through a fiber attached

to a detector by a fiber connector and adapter. The proximity ofa fiber connector to the detector and

its associated window provide an opportunity for reflections to introduce offsets in the power

readings. Even though the measurements using a fiber connector are generally repeatable, changing

connectors can skew the measurements results. We selected six common connector types (FC/PC,

FC/APC, ST, biconic, SC, and SMA) from four vendors chosen randomly. Calibrations were

performed on four types of power meters and at wavelengths of 850, 1310, and 1550 nm. We found significant measurement offsets resulting from the use ofvarious connectors and a

variability within a single connector type obtained from different vendors. Thus, possible errors could likely occur when changing types of connectors or connector vendors on fibers connected

to OFPMs. For accurate calibration measurements, meter owners should be aware of the

14
connector effects. A laboratory standard such as a thermal device, whose output is insensitive to

the connector types, is a useful tool when determining effects due to various connectors. The

connector adapter used with the connector is an integral part of the measurement.

The magnitude of the connector-induced offset is wavelength-dependent. The offset is small if a connector has low reflectivity or if the power meter sensor is angled. Also, antireflection coatings can help minimize this effect. It is very important to calibrate an OFPM with the same type of

connector used in the actual measurement.

4. Uncertainty Assessment

In this section we will assess the uncertainty for the optical fiber power measurement system. The

uncertainty estimates for the NIST optical fiber power measurements are described and combined

using the referenced guidelines [16]. To establish the uncertainty limits, the uncertainty sources

are separated into Type A, whose magnitudes are obtained statistically from a series of

measurements, and Type B, whose magnitudes are determined by subjective judgement.

The Type A uncertainty components are assumed to be independent and, consequently, the

standard deviation, for each component is

S. =

^ N

N-1

(2)

where the x values represent the individual measurements and N is the number of x values used

for a particular Type A component. The standard deviation of the mean is S/N'^\ and the total

standard deviation of the mean is [S(Sr^/N)]'^\ where the summation is carried out for all Type A

components.

All the Type B components are assumed to be independent and have rectangular or uniform

distributions (that is, each has an equal probability of being within the region, ±6^, and zero

probability of being outside that region). If the distribution is rectangular, the standard deviation,

Og, for each Type B component is equal to 6/3'''' and the total 'standard deviation' is (SOg^)'"'', where the summation is performed over all Type B components.

The combined uncertainty is determined by combining the Type A and Type B standard deviations

in quadrature; the expanded uncertainty is obtained by multiplying this resuh by a coverage factor

of 2. The expanded uncertainty, U, is then

15
Yo'^y^ (3)

r ^ r N

The number of decimal places used in reporting the mean values of the calibration factor are determined by expressing the expanded NIST uncertainty to two significant digits.

In Tables 5 through 7, we describe the OFPM calibration uncertainty using Type A and Type B

components. Items a-f (for Type B components) do not change in the uncertainty assessment,

while item g depends on specific calibration conditions.

Type A:

a. Laser power stability: During the calibration of an OFPM, fluctuations in the splitting ratio of

power going to the test detector (or ECPR) and the monitor detector can cause a possible error. Also, since the monitor detector and the ECPR have different time constants, a rapidly fluctuating

laser diode source can cause an uncertainty in the system ratio measurement. The power stability

uncertainty is estimated by observing the 'before' and 'after' (calibration) ECPR readings relative

to the monitor output. The difference is recorded and used for the uncertainty calculation. The

laser stability standard uncertainty is equal to the difference in the two system ratios. The

standard uncertainty changes for each particular calibration.

b. Repeatability: This is an uncertainty due to the scatter of data points around the measurement

average obtained from the series of calibration runs (usually six) on the OFPM being calibrated.

TypeB:

a. Ancillary electronics: This uncertainty is due to the combined effect of possible errors in the

electronic equipment used in the electrical and laser measurements (the standard uncertainty is 0.01 %), and a misalignment of the ECPR chopper (the standard uncertainty is 0.04 %). The

values for standard uncertainties are obtained from reference [9] and manufacturers' manuals [17-

18]. These values are listed in Tables 3 through 5. The combined standard uncertainty is equal to

0.04 %.

b. LOCR: This uncertainty consists of two primary components: window transmittance and

cavity absorptivity. The window transmittance is measured at several location on the window

before and after the calibration. The cavity absorptivity uncertainty is due to radiation which

scatters or reflects from the LOCR and, consequently, does not contribute to heating the cavity.

The cavity is constructed to minimize this effect as well. The standard combined uncertainty is equal to 0.02 % as described in reference [11].

c. ECPR linearity: This uncertainty is due to the different powers during the calibration of the

ECPR against LOCR and actual calibration of a power meter against the ECPR. The magnitude

U = 2

^

16
of this uncertainty is based on an evaluation of past results in Appendix G that gives the largest

difference in calibration factors between calibrations at 0.5 and 1.0 mW. The difference is 0.06

%. Thus, the standard uncertainty is 0.06/(2/3) = 0.02 %.

d. ECPR spectral responsivity: This uncertainty is due to the ECPR being somewhat wavelength

sensitive. The ECPR is calibrated against the LOCR at wavelengths of 633, 1319, and 1 550 nm,

but it is used at other wavelengths: 672, 786, 852, 986, 1307, and 1550 nm. Measurements

showed small spectral effects between 1319 and 1550 nm for the ECPR (see Table 1). The

maximum calibration factor difference is 0.33 % between 633 nm and 1319 nm. We use a linear

interpolation for the ECPR calibration factors at 672, 786, 852 and 986 nm. The standard

uncertainty in this region is 0.33/(2/3) = 0. 10 %. In the wavelength region between 1319 and

1550 nm, the standard uncertainty is less than 0.01 % (see Table 1).

e. ECPR uniformity: In addition to the calibration uncertainties listed above, the ECPR has a nonuniform spatial response that can cause a possible error in measurements. The magnitude of

this is estimated by performing spatial uniformity scans (see Appendix H). We assume that due to misalignments of a laser beam in the radius of 0.5 mm, the maximum spread is 0. 13 %. The

standard uncertainty is 0. 1 3/(2/3) = 0.04 %.

f Connector: This uncertainty is due to effects caused by a fiber connector on the ECPR. The

ECPR is calibrated against the LOCR using a coUimated beam, but is used with fiber connectors

to calibrate customers' power meters. We compared our ECPR with several pyroelectric trap

detectors at various wavelengths using both a coUimated beam and a FC/PC fiber connector.

Four measurements were performed. The largest difference between the coUimated beam and

connectorized measurements is 0.34 %. The standard uncertainty is 0.34/(2/3) = 0. 10 %. Note:

this approach does not 'protect' from 'the-worst case scenario' — interchanging different types of

connectors, power meters and connectors from different manufacturers at random. We assume

that the power meter owner utilizes the same fiber cable, connectors and connector adapters used

by NIST during the calibration of the power meter.

g. Test meter wavelength effect: This uncertainty is due to the drift in the source wavelength. The

magnitude of this effect is proportional to the wavelength uncertainty times the spectral response

gradient of the test detector at the wavelength being used. This uncertainty can be quite large if the spectral response curve is changing rapidly (e.g., Ge detectors in the 1550 nm region). NIST

keeps a history file on all OFPM system laser wavelengths. The wavelength uncertainty value for a specific test meter is found by assuming that the standard uncertainty of the OSA is 0. 13 nm

including the instrument drift. A typical spectral responsivity curve (see Table 3) for the test meter is used. Typical spectral responsivity slopes (%/nm) are given in Table 3.

17
Table 3. Spectral responsivity slope (%/nm) for Si, Ge, and InGaAs

detectors.

Diode Type Wavelength (nm)

670 & 780 850 & 980 1300 1550

Si 0.31 0.14 NA NA

Ge NA 0.48 0.14 0.92

InGaAs NA 0.53 0.09 0.05

Table 4 gives standard uncertainty values for Si, Ge, and InGaAs detectors. We combine the

OSA uncertainty with the sources' wavelength drift value from Appendix D. The standard

uncertainty due to this wavelength effect is equal to the appropriate value from Table 3 multiplied

by the combined uncertainty of the OSA and the source wavelength drift value from Appendix D.

Tables 5 through 7 list typical measurement uncertainties for calibrations of OFPMs which use Si,

Ge, and InGaAs detectors, respectively. The exact values of these various components change

for the particular measurement conditions at the time of the measurement.

Table 4. Standard uncertainty (%) for spectral responsivity for Si, Ge, and InGaAs

detectors.

Diode Type

670 780

Wavelength (nm)

850 980 1300 1550

Si 0.05 0.10 0.04 0.02 NA NA

Ge NA NA 0.13 0.06 0.03 0.15

InGaAs NA NA 0.14 0.07 0.02 0.01

18
Table 5. Typical measurement uncertainties for a Si detector at 850 nm.*

Source Standard uncertainty (type)

(%)

Electronics 0.04 (B)

LOCK 0.02 (B)

ECPR linearity 0.02 (B)

ECPR spectral responsivity

@ 850 nm 0.10(B)

ECPR uniformity 0.04 (B)

Connector 0. 10 (B)

Laser power stability 0.06 (A)

Test meter spectral responsivity

0 04

Repeatability (N = 6)

@ 850 nm 0.12/V"6(A)

Combined uncertainty

@ 850 nm 0.178

Expanded uncertainty (k = 2)

@ 850 nm 0.36

* For other wavelengths, the appropriate test meter spectral responsivity (Table 4) is substituted.

** For the collimated beam measurements, the connector-related uncertainty is equal to

zero.

19
Table 6. Typical measurement uncertainties for a Ge detector at 1300 nm.

Source Standard uncertainty (type)

(0/.

Electronics 0.04(B)

LOCK ^ 0.02(B)

ECPR linearity 0.02(B)

ECPR spectral responsivity

@ 1300 nm 0.01 (B)

ECPR uniformity 0.04(B)

Connector** 0.10(B)

Laser power stability 0.04 (A)

Test meter spectral responsivity

@ 1300nm 0.03(B)

Repeatability (N = 6)

@ 1300nm 0.07/V6(A)

Combined uncertainty

@ 1300nm 0.132

Expanded uncertainty (k = 2)

@ 1300nm 0.26

* For other wavelengths, use appropriate the ECPR spectral responsivity uncertainty (item

d, p. 17) and appropriate test meter spectral responsivity (Table 4).

** For the coUimated beam measurements, the connector-related uncertainty is equal to

zero.

20
Table 7. Typical measurement uncertainties for an InGaAs detector at 1550 nm.*

Source Standard uncertainty (type)

Electronics 0.04 (B)

LOCK 0.02 (B)

ECPR linearity 0.02(B)

ECPR spectral responsivity

@ 1300 & 1550 nm 0.01(B)

ECPR uniformity 0.04 (B)

Connector** 0.10(B)

Laser power stability 0.06 (A)

Test meter spectral responsivity

@ 1550nm 0.01(B)

Repeatability (N = 6)

@ 1550 nm 0.22//6(A)

Combined uncertainty

@ 1550nm 0.161

Expanded uncertainty (k = 2)

@ 1550nm 0.32

* For other wavelengths, use appropriate the ECPR spectral responsivity uncertainty (item

d, p. 17) and appropriate test meter spectral responsivity (Table 4).

** For the coUimated beam measurements, the connector-related uncertainty is equal to

zero.

21
5. Future Work

Even though the ECPR is the laboratory standard at this time, improved pyroelectric and quantum

detectors are now being developed and may eventually replace the current instrument. The

wavelength uncertainty could be decreased by introducing laser-stabilizing Bragg gratings that

lock the laser diode output wavelength to the Bragg wavelength of the fiber grating. At the

present time, the measurement system can accommodate most commonly used connector types.

Because of the constantly changing measurement requirements (new wavelengths, power levels

and connector types), we have to upgrade our capabilities fi"om time to time. There is an effort to

modernize the existing calibration software as well.

This work was supported in part by the Calibration Coordination Group (CCG) of the

Department of Defense and NIST's Calibration Services Development Fund. Kent Rochford,

Steven Mechels, and Jack Wang of NIST reviewed the manuscript, John Lehman ofNIST

provided useful insights on optical fiber power meters' spectral-responsivity measurements and

transfer standards; the authors thank them for their valuable comments.

6. References

[1] Laser power and energy, in Natl. Inst. Stand. Technol. Spec. Publ. 250, 98-103, 1998.

[2] Gallawa, R. L.; Li, X. Calibration of optical fiber power meters: The effect of connectors.

Appl. Opt. 26(7): 1170-1174, April 1, 1987.

[3] Vayshenker, I.; Li, X.; Keenan, D.; Scott, T.R. Errors due to connectors in optical fiber

power meters. Natl. Inst. Stand. Technol. Spec. Publ. 905, 49-52, 1996.

[4] Vayshenker, I.; Li, X.; Keenan, D.; Scott, T.R. FO connector types affect power

measurements. Test Meas. World, 23-25; February 1997.

[5] Cambridge Research and Instrumentation, Inc., 21 Erie Street, Cambridge, MA 02139.

[6] Foukal, P. v.; Hoyt C; Kochling H.; Miller P. Cryogenic absolute radiometers as laboratory

irradiance standards, remote sensing detectors, and pyroheliometers. Appl. Opt. 29(7): 988-

993; 1990.

[7] Johnson, B. C; Kumar, A.R.; Zhang, Z. M.; Livigni, D.J.; Jones, R.D.; Scott, T. R. Heat

transfer analysis and modeling of a cryogenic laser radiometer. J. Thermophys. Heat Trans.

12(4): 575-581, October-December 1998.

22
[8] Livigni, D.J.; Cromer, C.L.; Scott, T.R.; Johnson, B.C.; Zhang, Z.M. Thermal

characterization of a cryogenic radiometer and comparison with a laser calorimeter.

Metrologia 35(6), 819-827; 1998.

[9] Hamilton, C.A.; Day, G.W.; Phelan, R.J. Jr. An electrically calibrated pyroelectric radiometer

system. Nat. Bur. Stand.(U.S.) Tech. Note 678; March 1976.

[10] Wolfe, W.L.; Zissis, G.J., eds. The Infrared Handbook. Washington, DC: Environmental

Research Inst, of Michigan, 7-79; 1985.

[11] Livigni, D.J. High accuracy laser power calibration service. To be published as Natl. Inst. Stand. Technol. Spec. Publ. 250-55.

[12] Livigni, D.J.; Li, X. Spatial uniformity of optical detector responsivity. Proc, National.

Conference of Standards Laboratories Workshop & Symp., Session 5A, 337-352; JulyAugust 1994.

[13] International Standard: Calibration of fibre optic power meters. CEUJEC 1315; 1995.

[14] Vayshenker, I.; Yang, S.; Li, X.; Scott, T.R.; Cromer, C.L. Optical fiber power meter

nonlinearity calibrations at NIST. To be published as Natl. Inst. Stand. Technol. Spec.

Publ. 250-56, 2000.

[15] Vayshenker, I.; Li, X.; Scott, T.R. Optical power meter calibration using tunable laser

diodes. Proc, National Conference of Standards Laboratories Workshop & Symp., Session

5A, 362-372; July-August 1994.

[16] Taylor B.N.; Kuyatt, C.E. Guidelines for evaluating and expressing the uncertainty ofNIST

measurement resuhs. Natl. Inst. Stand. Technol. Tech. Note 1297; September 1994.

[17] Hewlett-Packard 3457 muhimeter operating manual. 1-11; 1986.

[18] Laser Precision Corp. RS-5900 electrically calibrated pyroelectric radiometer instruction

manual, 33-34; 1982.

23
Appendix A. Laser Diode Optical Spectra

100

° 80

-*—>

C/) c

(D

CD>

a:

60

40

20

0

1290

1

. D / 4 — 1 1295 1300 1305 1310

Wavelength (nm)

1315

Figure A-1. Optical spectra of a typical laser diode used in the OFPM calibration system.

24
Appendix B. Measurement Flow Chart

START"

SYSTEM COMMON,

MAIN VARIABLES

mmALIZE GPIB CARD

coNncuRATing

nescRipnoN

SELECT TEST MErTER FROM THE LIBRARY

MEASURE MONITOR'S AND ECPR'S BACKGROUND

MEASURE FIRST SYSTEM RATIO KOWnjR VS. ECPR USING CHOPPER

MEASURE TEST ^ETER

BACKGROUND

CAUBRATE TEST >eTER VS. MONITOR <CW>

MEASURE SECOND SYSTEM RATIO KIWTDR VS. ECPR USING CKIPPER

' YES

CALCULATE TEST METER CAUBRATIDN FACTDR

PRINT DATA SHEET FDR CALIBRATION REPORT

25
Appendix C. Sample of a Calibration Report

U.S. DEPARTMENT OF COMMERCE

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY

ELECTRONICS & ELECTRICAL ENGINEERING LABORATORY

Boulder, Colorado 80303

REPORT OF CALIBRATION for

OPTICAL POWER METER

Meter's Manufacturer

Model Number

Serial Number

with Sensor

Model Number and Serial Number

Submitted by:

Company Name

Address

Calibration Summary

The test optical power meter and the associated sensor was calibrated at wavelengths of 851.9, 1307.0,

and 1549.6 nm (with a 0.13 nm standard uncertainty) by comparing it to a calibrated laboratory standard

(see Figure 1). The NIST laboratory standard was an electrically calibrated pyroelectric radiometer

(ECPR) which had previously been calibrated against the NIST Laser Optimized Cryogenic Radiometer

(LOCK) system. The single-mode fiber with FC/PC connectors was supplied by the test meter owner. Before the measurements began, the instruments were allowed to reach equilibrium with the laboratory

environment and the zero setting was adjusted as specified by the manufacturer.

Table 1. Calibration results (Power: 100

Detector/

fiber type

Source

wavelength

(nm)

Meter

setting

(nm)

Calibration

factor

(reading/jiW)

Expanded

uncertainty

(k = 2)

(%)

Si/SM 851.9 851.9 0.9986 0.34

Ge/SM 1307.0 1307.0 0.9994 0.28

Ge/SM 1549.6 1549.6 0.9989 0.41

Folder No. & NISTID: 26100 & 815000

Date of Report: November 19, 1999

Reference: P.O. No. 100000 10/28/99 1 of 6

26
Meter's Manufacturer

Model Number

Serial Number

with Sensor

Model Number and Serial Number

The laboratory temperature during these measurements was 22°C (± 2°C) and the relative humidity was

11 % (± 3.5 %). The wavelength selection was set to the value listed in Table 1. The test meter

calibration factor was obtained by dividing its net display reading by the incident power.

The resuhs of this calibration are summarized in Table 1 . If the display readings of the test meter are divided by the calibration factor in Table 1, then, on the average, the resulting values will agree v^th the

NIST national reference standards.

EHgital

Voltmeter

Temperature

Controller

Laser Power

Supply

Sample

^^mt

Rotatable Mounting

Platform Positioning

Rail

Data Acquisition &

Analysis System

1550 mn

Plate

mm.

NISTECPR

chopper

User's fiber/connector

or collimated beam

BCD/GPIB

Converter I

NIST Standard

(ECPR)

User Test Meter

Figure 1 . Measurement system.

Folder No. & NISTID: 26100 & 815000

Date of Report: November 19, 1999

Reference: P.O. No. 100000 10/28/99 2 of 6

27
Meter's Manufacturer

Model Number

Serial Number

with Sensor

Model Number and Serial Number

Uncertainty Assessment

The uncertainty estimates for the NIST laser energy measurements are described and combined using the

referenced guidelines in NIST Technical Note 1297. To establish the uncertainty limits, the uncertainty sources are separated into Type A, whose magnitudes are obtained statistically from a series of

measurements and Type B, whose magnitudes are determined by subjective judgement.

The Type A uncertainty components are assumed to be independent and, consequently, the standard

deviation, S,, for each component is

S. = N

(1)

^ N-l

where the Xj values represent the individual measurements and N is the number of Xj values used for a

particular Type A component. The standard deviation of the mean is S/N'^\ and the total standard

deviation of the mean is [E(Sr^/N)]'''\ where the summation is carried out for all Type A components.

All the Type B components are assumed to be independent and have rectangular or uniform distributions

(that is, each has an equal probability of being within the region, ±6^, and zero probability of being

outside that region). If the distribution is rectangular, the standard deviation o„ for each Type B

component is equal to 6/3'"^ and the total "standard deviation" is (So,^)'''', where the summation is performed over all Type B components.

The combined uncertainty is determined by combining the Type A and Type B standard deviations in

quadrature; the expanded uncertainty is obtained by multiplying this result by a factor of 2. The expanded

uncertainty, U, is then

U = 2

S,^

> s r N

The values used to calculate the NIST expanded uncertainty (shown in Table 1) are listed in Tables 2 and

3. The number of decimal places used in reporting the mean values of the calibration factor listed in

Table 1 were determined by expressing the expanded NIST uncertainty to two significant digits.

Folder No. &NISTID: 26100 & 815000

Date of Report: November 19, 1999

Reference: P.O. No. 100000 10/28/99 3 of 6

28
Meter's Manufacturer

Model Number

Serial Number

with Sensor

Model Number and Serial Number

Table 2. NIST measurement uncertainties for Si detector at 850 nm.

Source Standard uncertainty (type)

Electronics 0.04 (B)

LOCK 0.02 (B)

Laboratory standard linearity 0.02 (B)

Laboratory standard spectral responsivity

@ 850 nm 0.10(B)

Laboratory standard uniformity 0.04 (B)

Connector 0.10(B)

Laser power stability 0.06 (A)

Test meter spectral responsivity

@ 850 nm 0.04 (B)

Repeatability (N = 6)

@ 850 nm 0.05//6 (A)

Combined uncertainty

@ 850 nm 0.17

Expanded uncertainty (k = 2)

@ 850 nm 0.34

Folder No. &NISTID:

Date of Report:

Reference:

26100 & 815000

November 19, 1999

P.O. No. 100000 10/28/99

29

4 of 6
Meter's Manufacturer

Model Number

Serial Number

with Sensor

Model Number and Serial Number

Table 3. NIST measurement uncertainties for Ge detector at 1300 and 1550 nm.

Source Standard uncertainty (type)

(%)

Electronics 0.04(B)

LOCK 0.02(B)

Laboratory standard linearity 0.02 (B)

Laboratory standard spectral responsivity

@ 1300 and 1550 nm 0.01(B)

Laboratory standard uniformity 0.04(B)

Connector 0.10(B)

Laser power stability 0.06 (A)

Test meter spectral responsivity

@ 1300 nm 0.03 (B)

@ 1550nm 0.15(B)

Repeatability (N = 6)

@ 1300nm . 0.07//6(A)

@ 1550 nm ' 0.12//6(A)

Combined uncertainty

@ 1300nm 0.139

@ 1550 nm 0.206

Expanded uncertainty (k = 2)

@ 1300 nm 0.28

@ 1550nm ' 0.41

Folder No. & NISTID: 26100 & 815000

Date of Report: November 19, 1999

Reference: P.O. No. 100000 10/28/99

30
Meter's Manufacturer

Model Number

Serial Number

with Sensor

Model Number and Serial Number

For the Director, Report Reviewed By:

National Institute of Standards

and Technology

Thomas R. Scott, Group Leader Christopher L. Cromer, Project Leader

Sources and Detectors Group Sources and Detectors Group

Optoelectronics Division Optoelectronics Division

Report Prepared/Calibrated By:

Igor Vayshenker, Electronics Engineer

Sources and Detectors Group

Optoelectronics Division

Folder No. &NISTID:

Date of Report:

Reference:

26100 & 815000

November 19, 1999

P.O. No. 100000 10/28/99

31

6 of 6
Appendix D. Wavelength History

This appendix describes the wavelength (in vacuum) history file for the lasers used in the optical

fiber power measurement system. All the measurements were taken with a calibrated optical

spectrum analyzer (OSA). Wavelength uncertainty is found by combining the OSA uncertainty

with the standard deviation of measured wavelength variation.

Table D-1 . Wavelength History File for the OFPM System's Lasers

Date Wavelength (nm)

11/92 672.3 786.3 841.0 NA NA NA 1306.7 1549.7

05/93 672.3 785.9 NA 852.1 NA NA NA 1549.6

02/94 672.3 785.5 840.9 852.3 NA NA 1307.2 1549.5

10/96 672.3 786.2 840.7 852.1 NA NA 1307.0 1549.7

07/97 672.2 785.8 840.6 851.9 NA 1304.2 1307.1 1549.4

02/98 672.1 786.1 840.4 851.6 NA 1304.3 1306.9 1549.6

08/98 672.1 785.6 840.5 851.8 NA 1304.3 1307.0 1549.6

11/98 672.2 786.2 840.6 851.8 NA 1304.3 1306.8 1549.6

03/99 672.3 786.1 840.6 851.7 986.0 NA 1307.0 1549.6

Average (nm) 672.2 786.0 840.6 851.9 986.0 1304.3 1307.0 1549.6

St. deviation

a,(nm)

0.09 0.30 0.21 0.24 NA 0.05 0.17 0.10

Wavelength

uncertainty

(0.125^+0,2)'/^

0.15 0.33 0.24 0.27 NA 0.14 0.21 0.16

32
Appendix £. Sample Results and Shipping Instructions for MAP

This appendix describes MAP preliminary results and shipping instructions.

The following results are preliminary for the MAP power meter S/N 2946G04047 that was

cahbrated at 851.9, 1307.0, and 1549.6 nm using customer supplied single-mode fiber with FC

connectors at both ends. The meter was set to 851.9, 1307.0, and 1549.6 nm. Both Si detector

(#255) and Ge detector (#133) were used. Si detector was used with laser wavelength of 85 1 .9 nm;

Ge detector was used with laser wavelengths of 1307.0 and 1549.6 nm. Time constant for Channel

A was set to 200 ms for both detectors. The offset was set to 0 dB. No lens was used.

Preliminary calibration factors using customer supplied fiber are as follows:

1.008 for 851.9 nm laser source using Si detector.

1.018 for 1307.0 nm laser source using Ge detector.

1.004 for 1549.6 nm laser source using Ge detector.

If the display or GPEB readings of the MAP meter are divided by these calibration factors, then the

resulting values will coincide with the NIST national standard. Please, fill out 'Sample Data Sheet'

for each of the wavelengths used and include any pertinent information for your standard.

More data will be collected after the instrument returns to NIST. We will submit a formal calibration

report at that stage.

SHIPPING INSTRUCTIONS

1 . When you receive our transfer standard locate and read the enclosed operating instructions.

2. After completing the measurements, please, send the transfer standard and your measurement

data to NIST (be sure to include the appropriate fiber cable(s), adapters, dust covers, etc.).

3. Ship to the following address:

National Institute of Standards and Technology

Attn: Igor Vayshenker/MS 815.01 (Rm. 3082C)

325 Broadway

Boulder, CO 80303

4. Before shipping back to NIST, securely pack the instrument. Disconnect all the plug-in

cables before shipping.

5. Insure the package for $10,000.

33
uos

00

-"^ ^

•o "5 i .S ^

CO 5 C 4i c &0 <u r,^ C^ C3

u, GO

4) "O g i

(Ulit

00 ;S

C (KJ ^

a. • '

c3 § 00 a, £ .c

«j 2>

u

.s § 13 00 .& ^ .S

P-I «

4> (U

00 On

34
Appendix G. ECPR Linearity Measurements

Table G-1. ECPR #483 calibrations against the

LOCR at different powers.

Average

power

(mW)

Calibration

factor

(reading/|iW)

N Standard

deviation

(%)

1.002 0.9887 4 0.01

0.502 0.9881 4 0.02

0.101 0.9886 5 0.13

The largest difference in calibration factors is between calibrations at 0.5 and 1.0 mW. The

difference is 0.061 %. The standard uncertainty is 0.061/(2/3) = 0.02 %.

35
Appendix H. ECPR Uniformity Scans

ECPR uniformity measurements performed by D. Livigni on ECPR #618 at a wavelength of 1557

nm.

Statistics for 2 mm beam with uniform centering error within ±0.5 mm of true center: The standard deviation is 0.03 %.

The spread (between minimum and maximum) is 0. 13 %.

Figure 1 . Surface plot of the entire dataset.

Figure 2. Surface plot around the detector's center.

36
THE SP 250 SERIES ON NIST MEASUREMENT SERVICES*

SP 250-1 Spectral Radiance Calibrations PB871 79883 SP 250-2 Far Ultraviolet Detector Standards PB87227609

SP 250-3 Radiometric Standards in the Vacuum Ultraviolet PB87227625

SP 250-4 Fricke Dosimetry in High-Energy Electron Beams

PB881 10374 SP 250-5 Alpha-Particle Calibrations PB881 68620 SP 250-6 Regular Spectral Transmittance PB881 08550

SP 250-7 Radiance Temperature Calibrations PB881 23674

SP 250-8 Spectral Reflectance PB881 09905

SP 250-9 Calibration of Beta-Particle-Emitting Ophthalmic

Applicators

PB881 08535 SP 250-10 Radioactivity Calibrations with the "4-n" Gamma

Ionization Chamber and Other Radioactivity

Calibration Capabilities

PB881 23708

SP 250-1 1 Dosimetry for High Dose Applications

PB88201587

SP 250-12 Neutron Personnel Dosimetry

PB87227617

SP 250-13 Activation Foil Irradiation with Californium

Fission Sources PB882 17443 SP 250-14 Activation Foil Irradiation by Reactor Cavity

Fission Sources PB88217435

SP 250-1 5 Photometric Calibrations PB881 53747 SP 250-1 6 Calibration of X-Ray and Gamma-Ray

Measuring Instruments PB88211826

SP 250-1 7 The NBS Photodetector Spectral Response

Calibration Transfer Program

PB88201595

SP 250-1 8 Neutron Source Strength Calibrations PB882 11818 SP 250-19 Calibration of Gamma-Ray-Emitting

Brachytherapy Sources PB891 93858 SP 250-20 Spectral Irradiance Calibrations PB881 23781 SP 250-21 Calibration of Beta-Particle Radiation

Instrumentation PB88201579

SP 250-22 Platinum Resistance Thermometer Calibrations PB881 38367 SP 250-23 Liquid-in-Glass Thermometer Calibration Service PB891 28888

SP 250-24 Standard Cell Calibrations PB881 23690

SP 250-25 Calibration Service for Inductive Voltage Dividers SP 250-26 NBS Phase Angle Calibration Services PB88225636

SP 250-27 AC-DC Difference Calibrations PB892222616

SP 250-28 Solid-state DC Voltage Standard Calibrations PB881 68703

SP 250-29 Traceable Frequency Calibrations PB881 68364

SP 250-30 GOES Satellite Time Code Dissemination:

Description and Operation

PB881 68760

SP 250-31 Mass Calibrations PB891 53894

SP 250-32 A Calibration Service for 30 MHz Attenuation and Phase Shift PB88238324

SP 250-33 A Calibration Service for Voltage Transformers and High-Voltage Capacitors

PB882252903

SP 250-34 High Vacuum Standard and Its Use

PB891 93841 SP 250-35 The Calibration of Thermocouples

and Thermocouple Materials PB89209340

SP 250-36

SP 250-37

SP 250-38

SP 250-39

SP 250-40 Absorbed-Dose Calibration of Ionization Chambers

A Calibration Service for Current Transformers PB91216770

Photometric Calibrations PB971 48472 NIST Leak Calibration Service PB921 49772 NIST Pressure Calibration Service PB94 164043

in a Co Gamma-Ray Beam

SN003-003-03034-1 $2.00

SP 250-41

SP 250-42

SP 250-43

SP 250-44

Spectroradiometric Detector Measurements:

Part I - Ultraviolet Detectors and

Part II - Visible to Near-Infrared Detectors SN003-003-03550-5 $9.50

Sprectroradiometric Detector Measurements:

Part III —Infrared Detectors SN003-003-03582-3 S5.25 Radiance Temperature Calibrations SN003-003-03511-4 $10.00

Radiation Processing Dosimetry Calibration Services and Measurement Assurance Program

SN003-003-03513-1

* Entries containing a stock number (SN003-003-) and price can be purchased from the Superintendent of Documents, U.S. Government

Printing Office, Washington, DC 20402-9325. GPO will accept checks, money orders, VISA, and MasterCard. For more infomation, or to place an order, call (202) 512-1800. Be sure to cite the stock number on all orders.

Entries containing PB numbers can be purchased from the National Technical Information Service, Springfield, VA 22161 . NTIS will accept

American Express in addition to the payment methods listed for GPO. For more information call (703)487-4650; to place an order call (800) 553-6487. Fax: (703) 321-8547. Be sure to cite the PB number on all orders.

Entries without stock or PB numbers are in preparation.
THE SP 250 SERIES ON NIST MEASUREMENT SERVICES* -Continued

SP 250-45 Radiation Processing Dosimetry Calibration Services: Manual of Calibration Procedures SN003-003-03514-9 $4.00

SP 250-46 NIST Multifunction Calibration System

SN003-003-03515-7 $2.75

SP 250-47 NIST Calibration Service for Capacitance

Standards at Low Frequencies SN003-003-03549-1 $7.00

SP 250-48

SP 250-49

Spectral Reflectance SN003-003-03545-9 $14.00 NIST Calibration Services for Gas Flow

Meters; Piston Prover and Bell Prover Gas Flow Facilities SN003-003-03560-2 $6.00

SP 250-51 Calibration Service of Optoelectronic

Frequency Response at 1319 nm for Combined Photodiode/rf Power Sensor

Transfer Standards SN003-003-03623-4 SP 250-52 Error Analysis and Calibration Uncertainty of Capacitance Standards at NIST SP 250-53 Calibration Service for Spectral Responsivity of Laser and Optical-Fiber Power Meters at Wavelengths Between 0.4 \x.m and 1.8 nm

SN003-003-03624-2 SP 250-54 Optical Fiber Power Meter Calibrations at NIST

SP 250-56 Optical Fiber Power Meter Nonlinearity Calibrations

at NIST

* Entries containing a stock number (SN003-003-) and price can be purchased from the Superintendent of Documents, U.S. Government

Printing Office, Washington, DC 20402-9325. GPO will accept checks, money orders, VISA, and MasterCard. For more infomation, or to place an order, call (202) 512-1800. Be sure to cite the stock number on all orders.

Entries containing PB numbers can be purchased from the National Technical Information Service, Springfield, VA 22161. NTIS will accept

American Express in addition to the payment methods listed for GPO. For more information call (703)487-4650; to place an order call (800) 553-6487. Fax: (703) 321-8547. Be sure to cite the PB number on all orders. Entries without stock or PB numbers are in preparation.


Technical Publications

Periodical

Journal of Research of the National Institute of Standards and Technology—Reports NIST research and

development in those disciplines of the physical and engineering sciences in which the Institute is active. These include physics, chemistry, engineering, mathematics, and computer sciences. Papers cover a broad

range of subjects, with major emphasis on measurement methodology and the basic technology underlying

standardization. Also included from time to time are survey articles on topics closely related to the Institute's technical and scientific programs. Issued six times a year.

Nonperiodicals

Monographs—Major contributions to the technical literature on various subjects related to the Institute's

scientific and technical activities. Handbooks—Recommended codes of engineering and industrial practice (including safety codes) developed

in cooperation with interested industries, professional organizations, and regulatory bodies. Special Publications—Include proceedings of conferences sponsored by NIST NIST annual reports, and

other special publications appropriate to this grouping such as wall charts, pocket cards, and bibliographies.

National Standard Reference Data Series—Provides quantitative data on the physical and chemical

properties of materials, compiled from the world's literature and critically evaluated. Developed under a

worldwide program coordinated by NIST under the authority of the National Standard Data Act (Public Law

90-396). NOTE: The Journal of Physical and Chemical Reference Data (JPCRD) is published bi-monthly for NIST by the American Chemical Society (ACS) and the American Institute of Physics (AlP). Subscriptions,

reprints, and supplements are available from ACS, 1155 Sixteenth St., NW, Washington, DC 20056.

Building Science Series—Disseminates technical information developed at the Institute on building

materials, components, systems, and whole structures. The series presents research results, test methods,

and performance criteria related to the structural and environmental functions and the durability and safety

characteristics of building elements and systems.

Technical Notes—Studies or reports which are complete in themselves but restrictive in their treatment of a

subject. Analogous to monographs but not so comprehensive in scope or definitive in treatment of the

subject area. Often serve as a vehicle for final reports of work performed at NIST under the sponsorship of other government agencies.

Voluntary Product Standards—Developed under procedures published by the Department of Commerce in Part 10, Title 15, of the Code of Federal Regulations. The standards establish nationally recognized

requirements for products, and provide all concerned interests with a basis for common understanding of the

characteristics of the products. NIST administers this program in support of the efforts of private-sector

standardizing organizations.

Order the following NIST publications—FIPS and NISTIRs—from the National Technical

Information Service, Springfield, VA 22161.

Federal Information Processing Standards Publications (FIPS PUB)—Publications in this series collectively constitute the Federal Information Processing Standards Register. The Register serves as the official source

of information in the Federal Government regarding standards issued by NIST pursuant to the Federal

Property and Administrative Services Act of 1949 as amended. Public Law 89-306 (79 Stat. 1127), and as implemented by Executive Order 11717 (38 FR 12315, dated May 11, 1973) and Part 6 of Title 15 CFR

(Code of Federal Regulations).

NIST Interagency Reports (NISTIR)—A special series of interim or final reports on work performed by NIST

for outside sponsors (both government and nongovernment). In general, initial distribution is handled by the sponsor; public distribution is by the National Technical Information Service, Springfield, VA 22161, in paper

copy or microfiche form.
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