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MOGlabs FZW600, Manual

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26

Chapter 5. Optical switcher

the output fiber is not accidentally sheered as it could break.

5.2

Operation

The

FSW4

and

FSW8

contain a

MEMS

mirror arrangement that

5.3

Software UI

When connecting to a

FZW

that has an optical switcher attached, the

interface will show a tabbed view for the different switcher inputs.

Names can be assigned to the inputs by double-clicking the tabs.

!

5.4

Simultaneous PID

!

Summary of Contents for FZW600

Page 1: ...Fizeau Wavemeter FZW600 Version 0 1 2 Rev 2 hardware ...

Page 2: ...uential damages in connections with or arising out of the performance or use of any of its products The foregoing limitation of liability shall be equally applicable to any service provided by MOGLabs Copyright Copyright c MOG Laboratories Pty Ltd MOGLabs 2017 2020 No part of this publication may be reproduced stored in a retrieval system or transmitted in any form or by any means electronic mecha...

Page 3: ...face 7 3 1 On board UI 7 3 2 Web UI 8 3 3 Software UI 9 4 Operation 15 4 1 Fringe identification and optimisation 15 4 2 Auto exposure algorithm 18 4 3 Wide and fast modes 18 4 4 Pulsed laser measurement 19 4 5 Externally triggered mode 19 4 6 Measurement averaging 20 4 7 PID control 21 4 8 Calibration adjustment 22 5 Optical switcher 25 5 1 Overview 25 5 2 Operation 26 5 3 Software UI 26 i ...

Page 4: ...Firmware updates 31 C Command language 33 C 1 General functions 33 C 2 Display settings 34 C 3 Measurement settings 34 C 4 Camera settings 35 C 5 Optical switch 36 C 6 PID control 37 D Communications 39 D 1 Protocol 39 D 2 TCP IP 39 D 3 USB 41 E Dimensions 43 ...

Page 5: ...de fibres are strongly preferred although small core multi mode fibres up to 62 5 µm can be used at the expense of reduced accuracy 1 4 Input light with the supplied free space to fibre adapter Typi cally the FZW only needs a few microwatts to operate so high coupling efficiency is not required The saturation Figure 1 is a measure of the power reaching the detector The auto exposure algorithm tune...

Page 6: ...rmal equilibrium and full accuracy within 15 minutes of being turned on The most accurate results will be obtained in a well stabilised lab environment It is recommended that the FZW not be in thermal contact with any other equipment to prevent formation of thermal gradients Host connection The recommended mode of operation is using the WindowsTM host application chapter 3 which provides a simple ...

Page 7: ...th Figure 1 1 Collimated monochromatic laser light and Fizeau etalons cre ate interference patterns on an imaging detector The wavelength is calcu lated by combining measurements of the fringes from four different etalons A rough estimate of the wavelength is obtained directly from the fringe spacing to an absolute accuracy of one part in 100 This initial estimate is then improved by the phase of ...

Page 8: ...other wavemeters as a calibration source The FZW also integrates a modern 32 bit microprocessor and high resolution compact colour display Wavelength calculation is perfor med automatically on the device so that no host computer is required It is compact and can be powered from USB or even a rechargeable battery so you can move it around your lab and measure wavelength right where you are adjustin...

Page 9: ... layout The buttons are arranged as a directional pad with up down left and right buttons and an additional OK button in the centre In wavelength display mode the up down buttons change the display units and the left right buttons swap between different diagnostic modes see 3 1 Pressing OK opens the menu system The display includes a sleep mode which reduces the brightness when not in use Where th...

Page 10: ...cal device error LOCK Off PID analog output disabled Green PID locked Yellow PID engaged but not locked Red PID output saturated Blue Analog output error 2 1 1 Menu system The menu system allows for interactive control of the device without a computer interface Figure 2 2 It is started by pressing the OK button from the measurement display mode and exiting by pressing the left directional button F...

Page 11: ...fies this digit and using the left right keys changes which digit is selected Pressing OK again exits edi ting mode In particular it is useful for configuring the Ethernet settings in an networking environment where DHCP is disallowed Figure 2 3 In this situation an appropriate static IP should be allocated to the unit the gateway set as required by the network configuration and DHCP set to OFF Fi...

Page 12: ...pe B connector for powering and or communicating with the device When used to power the device must be connected to a USB port capable of supplying 600 mA Ethernet RJ 45 jack for 10 100 MB s TCP IP communications which is the recommended interface for computer control and monitoring SMA output Analog output port for wavelength monitoring or PID control of laser wavelength see 4 7 16 bit resolution...

Page 13: ...he saturation is a measure of the optical power reaching the de tector and the contrast is a measure of fringe quality In general higher saturation is preferred as this permits faster measurement however oversaturation as indicated by the bar turning red will degrade measurement accuracy Pressing the left right buttons changes to an alternate display mode Figure 3 2 permitting diagnostic of the fr...

Page 14: ...e for monitoring the device remotely through a web browser such as using a smartphone Na vigating to the device IP address displays the currently recorded wavelength which is automatically updated Figure 3 3 At present this interface doesn t provide control options but increased functio nality will be provided in future firmware updates Figure 3 3 Demonstration of the integrated web interface show...

Page 15: ...F 3 3 Software UI A fully featured control and diagnostic program suite for WindowsTM operating systems is available from the MOGLabs website Figure 3 4 Demonstration of the host software interface showing expo sure controls 1 convergence monitor 2 interference fringes 3 measu red wavelength 4 display units selector 5 and device diagnostics 6 The font size of the measured wavelength can be enlarge...

Page 16: ...iably In situations where the laser wavelength is changing rapidly or the calibration has been perturbed the bars may exceed the indicated region indicating the reliability of the me asured value is reduced 3 3 1 Time series measurement Clicking the Time series button on the lower left of the window brings up a dialog that shows how the measured wavelength is chan ging over time Figure 3 5 This ca...

Page 17: ...th measu rement is changing over time for measuring drift The graph displays Duration seconds of data with a datapoint collected every Interval se conds When Averaging is enabled the wavelength measurements during each interval are averaged to enhance the measurement precision ...

Page 18: ... configured for maximum measurement speed the FZW can be used to measure the mode hop free scan range of a laser Set ting the Interval to zero ensures measurements are recorded as rapidly as possible as indicated by the label in the bottom left ...

Page 19: ...enient interface for optimising the gain values and verifying the state of the control loop When the control loop has saturated at one of its limits the box will be highlighted in magenta Figure 3 7 Interactive window for adjusting the PID constants including display of the instantaneous PID error value in MHz and the output value in Volts for diagnostic purposes ...

Page 20: ...14 Chapter 3 User interface ...

Page 21: ...uring a measure ment can change the structure of the interference pattern and cause the measurement to fail Typically this is evident by the presence of secondary peaks in the fringes a significant widening of the peak widths and or a significant reduction in the amplitude of the fringes compared to the background level Figure 4 1 Multimode behavi our may be evident in only one of the etalons Figu...

Page 22: ... a non Gaussian beam shape that introduces bias and reduces accu racy of the measurement Single mode fibres are therefore strongly preferable where accurate measurements are required With multimode fibre the structure of the fringes fluctuates with both the fibre coupling alignment and mechanical strain on the fibre as can be seen by fluctuations in the measured wavelength when dis turbing the fib...

Page 23: ...causes measurement bias left Adjusting the input coupler alignment can give more uniform fringe heights right and more reliable measurement Figure 4 4 Examples of fringes measured with a 200 µm core fibre The mode shape makes reliable readout almost impossible left although in some situations a low accuracy measurement can still be achieved right ...

Page 24: ...to disable the auto expose feature 4 3 Wide and fast modes The default measurement mode is suitable for most applications and provides a good general purpose trade off between measure ment speed and accuracy However in some situations it may be preferable to deliberately reduce the device accuracy to increase the measurement rate or reduce susceptibility to unstable or high linewidth input lasers ...

Page 25: ...scenario from ocurring Note however that global shutter mode is not recommended for CW lasers as it tends to result in distortion from an effective over exposure towards the bottom of the CCD 4 5 Externally triggered mode The FZW includes a TTL input for externally triggering an acquisi tion This is particularly useful when measuring pulsed lasers with low repetition rates which can help ensure th...

Page 26: ...but the influence of drift increases A typical Allan deviation measurement Figure 4 5 shows that the measurement precision can be improved by up to 250 ms of averaging The limiting factor which causes drift on longer timescales is small fluctuations in the device temperature at the 0 05 C level The internal averaging can be configured using the MEAS AVERAGE command Setting the value to zero disabl...

Page 27: ...dτ Kd de t dt V0 where e t f t f0 is the error function the difference between the measured laser frequency and the setpoint frequency in MHz The PID constants are in the range 1 1 and G represents an overall gain in MHz V These values can be set using the PID GAIN command as shown in the example below or using the software interface see 3 3 3 The range of the analog output is 2 5 V with an offset...

Page 28: ... over a very wide range of wavelengths 400 1100 nm and its absolute accuracy over this range is limited by a variety of broadband effects The FZW does not include an internal calibration source because the inherent stability of the FZW across the full wavelength range is better than the accuracy of compact references such as a neon lamp However often the accuracy of a wavemeter is only critical ar...

Page 29: ...entered known laser frequency in THz This calibration correction can also be applied programmatically using the MEAS CORRECT command Note that when adjusting the calibration it is recommended to use a well known reference e g atomic transition with an appropriate amount of averaging The calibration can also be reverted to the factory provided cali bration by ticking the appropriate box in the soft...

Page 30: ...24 Chapter 4 Operation ...

Page 31: ...ve the SMA outputs for monitoring and PID control Pressing the front panel buttons cycles between the input fibers The switcher can be controller through software commands or with the physical push buttons permitting both standalone and automa ted operation LEDs on the front indicate the active channel and separate SMA outputs on the back provide individually configurable PID outputs for each chan...

Page 32: ...eration The FSW4 and FSW8 contain a MEMS mirror arrangement that 5 3 Software UI When connecting to a FZW that has an optical switcher attached the interface will show a tabbed view for the different switcher inputs Names can be assigned to the inputs by double clicking the tabs 5 4 Simultaneous PID ...

Page 33: ...Up to 350 meas s Number of etalons 4 Smallest etalon FSR 7 5 GHz Electronics DC jack power input 5 V Rev 1 3 or 9 24 V Rev4 as labelled on device Power usage 3 W Display Integrated colour LCD screen Analog output 12 bit DAC output 2 5 V range 1 Absolute accuracy as measured in a temperature stabilised laboratory envi ronment using a spectrally narrow laser coupled into single mode fibre 2 Stated o...

Page 34: ...USB B plug Optical input FC PC or FC APC as labelled on device Control software Integrated on device menu system WindowsTM software suite Integrated web server Language bindings Examples provided for python MATLAB LabVIEW Mechanical Dimensions W H D 146 120 81 mm Weight 1 5 kg Optical switcher specifications ...

Page 35: ...29 0 10 20 30 40 50 60 70 350 450 550 650 750 850 950 1050 1150 Wavelength nm Quantum Efficiency Figure A 1 Typical detector responsivity ...

Page 36: ...30 Appendix A Specifications ...

Page 37: ...nsure the serial number matches the device 2 Press the Select button to choose a firmware package to use as downloaded from the MOGLabs website 3 The package is compared against the currently running version to determine which upgrades are required Figure B 2 Up to date components are shown in green upgrades are shown in yellow downgrades in purple and conflicts in red 4 Click on Update all to ins...

Page 38: ...t firmware versions 2 Click the Select button 3 to open a firmware package for upload Figure B 2 The firmware update application with a loaded package The versions running on the device are compared against the selected package in this instance showing that an update is available for the IAP yellow and the other components are up to date green ...

Page 39: ...the most recent version of the manual available at http www moglabs com Some commands accept values with units The following units are recognised for returning measurements or defining setpoints nmv vac Wavelength in vacuum in nanometers nma air Wavelength in air in nanometers as measured within the interfero meter May differ from expected standard temperature and pressure STP value due to environ...

Page 40: ...wavelength in the specified units UNITS MEAS UNITS units Set the default units for measurement readback as well as the units used by the integrated LCD display SAT MEAS SAT Returns the measurement saturation which is a number in the range 0 100 that measures the optical power reaching the detector Typi cally the saturation should be in the range 50 90 to ensure enough light for rapid measurement b...

Page 41: ... is performed CLEAR MEAS CLEAR Reset the measurement averaging and internal verification for use in combination with an external optical switch or shutter CORRECT MEAS CORRECT val Apply a correction to the device internal calibration using the currently supplied laser as an absolute reference The reference value val should be specified in THz and as many significant figures as practi cal Perturbin...

Page 42: ...ack when the light is coupled back in Reducing the maximum exposure time can improve the device s apparent responsiveness in this situation GAIN CAM GAIN value Set query the camera analog gain which is an integer in the range 8 126 Increasing the gain allows the exposure time to be reduced for the same optical power enabling an increased measurement rate The effective increase in measured counts i...

Page 43: ...z GAIN PID GAIN val Set query the overall gain used for the PID controller in MHz V KP KI KD PID KP val or PID KI val or PID KD val Set query the PID coefficients Kp Ki and Kd which are floating point values in the range 1 1 OFFSET PID OFFSET val Set query the constant DC offset on the analog output in volts MIN PID MIN val Set query the minimum output voltage of the PID controller MAX PID MAX val...

Page 44: ...38 Appendix C Command language ...

Page 45: ... strongly recommended that all software should wait for this response and check for success before continuing The python and LabVIEW bindings provided take care of buffering and error checking automatically The MOGLabs Commander application mogcmd is available as part of the mogfzw package and provides a convenient interface for sen ding commands and receiving responses Figure D 1 D 2 TCP IP The F...

Page 46: ... settings are stored in the non volatile memory of the unit and will be recalled in future 1 From the main menu open Options Ethernet Settings 2 Select Static IP and use the buttons to set the IP address of the device as required 3 Select Gateway and set the gateway address as required 4 Select DHCP and set to OFF 5 Select Restart ethernet and press the OK button 6 The new IP address will be displ...

Page 47: ...ist of devices including Ports Figure D 2 Figure D 2 Screenshot of Device Manager showing that the FZW can be communicated with using COM4 The port number might change when plugging into a different USB port or after applying a firmware update The device can be identified as a COM port with the following name STMicroelectronics Virtual COM Port COMxx where xx is a number typically between 4 and 15...

Page 48: ...re the wavemeter is disconnected from the computer 2 Run the 32 bit or 64 bit USB driver setup program from the package as appropriate for your computer system note that all modern computers are 64 bit 3 Reconnect the wavemeter using the USB cable The device driver will be activated which may take up to a minute 4 The device should be installed as an Virtual COM Port as described above 5 Run the m...

Page 49: ...E Dimensions 83 120 146 32 43 ...

Page 50: ...44 ...

Page 51: ......

Page 52: ...aboratories Pty Ltd 49 University St Carlton VIC 3053 Australia Tel 61 3 9939 0677 info moglabs com c 2017 2020 Product specifications and descriptions in this do cument are subject to change without notice ...

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