Santec PEM-320 User manual

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PEM-320
Polarization Extinction Ratio Meter
Operation Manual

PEM-320 Operation Manual
This product has been produced in accordance with ISO-9001 international
quality system standards.
Disclaimer
Every effort has been made to ensure the information contained in this manual is accurate and easily
understandable. Santec shall not, however, be liable for errors contained herein, or for incidental or
consequential damages in connection with the use of this material.
Copyright 2000, Santec Corporation, Japan. No part of this document may be reproduced, stored in a
retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying,
recording, or otherwise without the prior written permission of Santec Corporation, Japan.

POLARIZATION EXTINCTION RATIO METER PEM-320
This manual explains the operation and safety features of the PEM-320 Polarization Extinction Ratio
Meter. To ensure the safe operation of the instrument, and to prevent the risk of personal injury and/or
damage to the equipment we recommend that you read the manual fully before commencing
installation and operation. In particular Chapter 6 outlines the precautions necessary to ensure safe
operation. The following safety symbols are used throughout the manual and on the equipment to
indicate safety related information.
DANGER!!
CAUTION
Packing Materials
The original packing materials are required to ensure the safe long term storage and safe transportation
of this equipment. It is recommended that all packing materials are kept for these purposes.
This indicates a dangerous procedure that could result in serious injury or
death if not performed properly.
This mark is used on the equipment as a warning of danger.
About This Manual
This indicates a hazardous procedure or danger that might result in injury or
that could damage the equipment if proper precautions are not taken.

PEM-320 Operation Manual
About This Manual
1. Introduction
2. Specifications
3. Features
3.1. Real Time Display
3.2. Offset Cancel
3.3. Communication Interfaces
3.4. Analogue Data Output
3.5. Stopped Polarizer Function
3.6. High Speed Measurement
4. Principle of Operation
5. Panel Descriptions
5.1. Front Panel
5.2. Rear Panel
6. Safety Information
6.1 Mains Voltage
6.2 Installation
6.3 Safe Operation
Contents

POLARIZATION EXTINCTION RATIO METER PEM-320
7. Operation Procedures
7.1. Power On
7.2. Optical Fiber Connection
7.3. Offset Cancel
7.4. Changing Display Units
7.5. PER Averaging Function
7.6. Analogue Output
7.7. Changing the Optical Connector
8. Communication Interfaces
8.1. GPIB Control
8.2. RS-232C Control
8.3. Control Commands
9. Example Programs
9.1. GPIB Program
9.2. RS-232C Program
10. Care and Maintenance
10.1. Care
10.2. Maintenance
10.3. Changing the Fuse
11. Troubleshooting
12. Warranty

PEM-320 Operation Manual

POLARIZATION EXTINCTION RATIO METER PEM-320
1-1
1Introduction
The PEM-320 Polarization Extinction Ratio Meter provides accurate, real-time information about the
polarization state of light in an optical fiber. It can be used as a general purpose measuring instrument
but has been designed, in particular, to enable the accurate and rapid alignment of polarization
maintaining fibers to optical components. The rotating polarizer design, coupled with a high
sensitivity detector enable the PEM-320 to measure high linear polarization extinction ratios, of up to
40dB, with a 2.5Hz refresh rate.
The PEM-320 simultaneously displays values for polarization extinction ratio (PER), optical power
and polarization angle. These are the three critical parameters required for the alignment of
polarization maintaining fiber to optical components. In addition, the PEM-320 has full support
for GPIB and RS-232C communication interfaces together with an analogue data output. These
features provide the unit with unrivalled flexibility for integration into automatic measurement and
automatic fiber alignment systems.
The PEM-320 is easy to use, but to obtain the most from your unit we recommend that you read this
manual fully and become familiar with its contents prior to operation. We hope that you will be
satisfied with your purchase.

1-2
PEM-320 Operation Manual

POLARIZATION EXTINCTION RATIO METER PEM-320
2-1
2Specifications
* The following options are available:
Wavelength Range 980nm, 1310nm, 1480nm & 1550nm bands.
Connector Polish SPC or APC
High Power Range -20dBm ~ 23dBm
The following items should be supplied with your PEM-320 unit:
1. 2 power switch keys.
2. Power supply cable.
3. Analogue interface (AIF) connection cable.
3. Operation manual.
4. Test report.
Item Unit Value
Wavelength Range nm 1520 ~ 1600* (power calibrated at 1550nm)
0 ~ 30 (when input power >-30dBm)
0 ~ 40 (when input power >-20dBm)
0.1 (when PER < 30dB)
0.3 (when PER > 30dB)
Power Measurement dBm -40 ~ +10*
0.1 (when Power > -30dBm)
0.3 (when Power < -30dBm)
Polarization Angle Resolution deg 0.45
Measurement Speed s 0.1, 0.2, 0.4 (selectable)
Operating Temperature ˚C 10 ~ 40
Connector Type - FC, SC (SPC polish)*
Communication Interface - GPIB, RS-232C
Size mm 210 x 80 x 300
Weight kg 3
Supply Voltage V 100 / 110 / 230 / 240
Maximum Power W 40
dBPower Resolution
PER Range dB
dBPER Resolution

2-2
PEM-320 Operation Manual

POLARIZATION EXTINCTION RATIO METER PEM-320
3-1
3Features
An Offset Cancel function is provided to enable compensation for the dark current of the
photodetector. This provides improved accuracy and greater dynamic range even when low optical
powers are used.
3.2. Offset Cancel
3.1. Real Time Display
The PEM-320 displays simultaneously, and in real time, values for the three critical parameters
required for the alignment and characterisation of polarization maintaining fiber and polarization fiber
pigtailed components. These are the polarization extinction ratio (PER), optical power and
polarization angle. In addition, the optical power can be displayed in units of mW or dBm.
The PEM-320 can be used as a stand alone bench-top type measurement instrument. However, it also
boasts industry standard GPIB and RS-232C interfaces through which the unit can be fully controlled
and through which all parameters can be monitored. The PEM-320 is thus suitable for automated
measurements in production environments and for integration into fully automatic alignment systems.
3.3. Communication Interfaces
In addition to the communication interfaces described above, the PEM-320 has an analogue output for
monitoring of all the measured parameters. These signals are particularly useful as feedback signals
for the control loops of automated alignment systems. As an option, an output monitoring the signal
directly from the photodetector can also be provided.
3.4. Analogue Data Output

3-2
PEM-320 Operation Manual
The PEM-320 measures PER using a rotating polarizer. In some circumstances, such as the automatic
alignment of the lateral orientation of an optical fiber to a laser light source, it is useful to be able to stop
the polarizer and measure the optical power with a faster response time than the 10Hz rotation will
allow. The Stopped Polarizer Function provides this flexibility and enables the polarizer to be stopped
at the angle of either maximum or minimum power transmission.
3.5. Stopped Polarizer Function
To provide additional flexibility the PEM-320 can operate at one of three measurement speeds. The
default 2.5Hz measurement speed is recommended as it provides the highest dynamic range for both
PER and optical power. However, when required, the measurement speed can be increased through
software control to either 5 or 10Hz.
3.6. High Speed Measurement

POLARIZATION EXTINCTION RATIO METER PEM-320
4-1
4Principle of Operation
The above diagram shows the design of the PEM-320 unit. The optical fiber is connected through the
input connector. The light from the fiber is then collimated by a lens, and after passing through a
rotating polarizer is incident on the photodetector. In units with the high power option fitted, an
optical attenuator is placed prior to the rotating polarizer. This attenuator is specially designed to be
polarization independent to ensure that it does not compromise the performance of the free space
optics design.
0180
1 measurement period
max
min
Optical Power
Polarizer Angle (deg)

PEM-320 Operation Manual
4-2
After amplification the detected signal is converted to a digital format to enable the measured
parameters to be calculated by the unit's microprocessor. The diagram on the previous page shows the
sine-wave signal obtained as the polarizer rotates. One measurement period corresponds to a 180˚
rotation of the polarizer. PER is calculated as the ratio of the maximum and minimum signals in any
one measurement period and the polarization angle is determined by detecting the position of the
polarizer at minimum transmission. The PEM-320 displays a polarization angle of zero when the
polarization axis is vertical and aligned with the alignment notch of the input connector.

POLARIZATION EXTINCTION RATIO METER PEM-320
5-1
5-1. Front Panel
5Panel Descriptions
(1) PER Display Panel
Displays the value for polarization extinction ratio (PER) in dB.
(2) Optical Power Display Panel
Displays the optical power. The measurement unit can be set to either mW or dBm and is toggled by
pressing the Optical Power Unit Selector Key (5). The power is calibrated at the center wavelength
of the operating range of the PEM-320 unit; i.e. at 980nm, 1310nm, 1480nm or 1550nm.
(3) Optical Power Unit Indicator
Indicates unit of optical output power (mW or dBm).
(4) Polarization Angle Display Panel
Indicates the polarization angle of the light from the optical input in degrees. The angle is
measured with respect to the alignment notch on the optical connector; i.e. a value of zero is given
when the polarization axis is vertical and aligned with the alignment notch.
(1) (2) (3) (4) (5)
(12) (11) (10) (9) (8) (7) (6)

5-2
PEM-320 Operation Manual
(5) Optical Power Unit Selector Key
Toggles the optical power measurement unit between mW and dBm. This key is also used when
setting the GPIB address and GPIB delimiter.
(6) Optical Input Connector
(7) GPIB Local Key / GPIB Address Change Key
a. Pressing this key when GPIB remote operation is active returns control to the front panel.
b. When this key is pressed for two seconds continuously the GPIB address and GPIB delimiter setting
mode is entered. The PER Display Panel (1) shows the GPIB address which flashes to indicate that
it can be changed using the Optical Power Unit Selector Key (5). Pressing the GPIB Local Key a
second time causes the GPIB delimeter setting shown in the Polarization Angle Display Panel (4) to
flash. Similarly, this can be changed using the Optical Power Unit Selector Key (5). Pressing the
GPIB Local Key a third time saves the displayed values and returns control to normal operation.
b. Pressing this key when the power to the PEM-320 is first switched on sets the RS-232C delimiter to
CR (carriage return).
(8) GPIB Remote LED
Indicates GPIB remote operation is active. When active the front panel keys become inoperative.
To return control to the front panel press the GPIB Local Key (7).
(9) Calibration Key (CAL)
Not used (reserved for future use).
(10) Zero Key (Offset Cancel)
a. Enables compensation for the dark current of the photodetector. A cover should be placed over the
Optical Input Connector to prevent any stray light entering the unit before this button is pressed.
b. Pressing this key when the power to the PEM-320 is first switched on sets the RS-232C delimiter to
LF (line feed).
(11) Serial Interface (SIF) Connector
Used for RS-232C communication.
(12) Power On / Off Key Switch
Operated using the power switch key, this is used to switch the unit on and off.

POLARIZATION EXTINCTION RATIO METER PEM-320
5-3
(1) Mains Connector Socket
(2) Fuse Housing
(3) Mains Voltage Indicator
The supply voltage is selected by removing the fuse housing cover, and rotating the mains
voltage indicator so that the correct voltage, corresponding to the mains supply voltage, is
shown in the window when the fuse housing cover is replaced. Ensure that the housing cover is
tightly closed before reconnecting the mains cord.
(4) Analogue Interface (AIF) Connector
Provides analogue output of PER, Optical Power and Polarization Angle.
(1) (2) (3) (4)
(7) (6) (5)
5.2. Rear Panel

5-4
PEM-320 Operation Manual
(5) Serial Number Label
Indicates model number, serial number and options installed on each unit.
(6) GPIB Connector
(7) Slit
Slit for heat dissipation. It is important to leave at least 5 cm of space behind the PEM-320 unit to
ensure proper ventilation and cooling.
100V ac
〜
remove drum
before turn
100V ac
〜
120V ac
〜
230V ac
〜

POLARIZATION EXTINCTION RATIO METER PEM-320
6-1
6
6.1. Mains Voltage
Safety Information
Please ensure the voltage indicated on the rear panel of the instrument corresponds with the
mains voltage supply. Applying an incorrect mains voltage will damage the equipment. See
Section 5.2 for details of how to change the voltage setting and Section 10.3 for details of
changing the fuse. Ensure that the rating of the fuse corresponds to the mains voltage selected;
details are given in Section 10.3.
The unit is provided with a three pin cord. To ensure the safe operation of the instrument please
make sure that this is connected to a grounded power outlet.
6.2. Installation
To ensure the safe operation of the instrument it should not be installed:
•In a position where the air from the cooling fan cannot flow freely. Allow at least 5cm
behind the unit for this purpose.
•Where there are high levels of vibration.
•Where it would come into contact with water.
•In very humid or dusty locations.
•Where there are strong electric or magnetic fields.
•In direct sunlight.
•Where there are extremes of temperature.