MOGlabs MWM User manual

MWM wavemeter
Revision3.19 mogwave 1.4.15 Firmware0.6.9

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Preface
The MOGLabs MWM wavemeter provides a compact, high resolution and
costeffective instrumentformeasuring thewavelengthand spectrumofa
laser. The instrument can be operated standalone, and easily controlled
fromacomputerwithasophisticatedhostapplicationorusingsimpletext
commands,viaUSB andethernet. Thelowpricemakesisaffordableeven
ifyouhavejustonelasertomeasure.
WehopethatyoufindtheMWMuseful,andpleaseletusknowifyouhave
anysuggestionsforimprovementoftheMWM orthisdocument,sothatwe
canmakelifeinthelabbetterforall.
MOGLabs,Melbourne,Australia
www.moglabs.com
i

ii

Contents
Preface i
1 Introduction 1
1.1 Basicsetup............................ 1
1.2 Softwareinstallation . . . . . . . . . . . . . . . . . . . . . . . 3
2 Standalone operation 5
2.1 On-devicemeasurements . . . . . . . . . . . . . . . . . . . . 5
2.2 Frontpaneldisplayandbuttons . . . . . . . . . . . . . . . . 5
2.3 Measuring............................. 6
2.4 Devicemenus........................... 7
3 Web interface 11
3.1 Homepage ............................ 12
3.2 Liveview.............................. 13
3.3 Live+................................ 14
3.4 Devicesetup............................ 14
3.5 Software.............................. 16
3.6 Updatefirmware......................... 16
4 MOGWAVE 17
4.1 Devicediscovery......................... 17
4.2 Maindisplay........................... 18
4.3 Menu................................ 20
4.4 Acquisition............................. 25
4.5 Options............................... 25
4.6 Wavelength............................ 26
4.7 Functions ............................. 27
4.8 Statusbar............................. 29
iii

iv Contents
5 Signal out and PID 31
5.1 MOGLabsDLC lasercontroller . . . . . . . . . . . . . . . . . 32
5.2 PIDparameters.......................... 32
5.3 Integratorwindup......................... 33
5.4 Examples.............................. 34
6 Calibration 37
6.1 Existingwavelengthrange . . . . . . . . . . . . . . . . . . . 37
6.2 CalibratingwithMOGLabsFZWwavemeter . . . . . . . . . 40
6.3 CalibratingwithHighFinessewavemeter . . . . . . . . . . . 40
6.4 Newwavelengthrange. . . . . . . . . . . . . . . . . . . . . . 41
6.5 Newfibre............................. 44
A Specifications 47
B Communications 51
B.1 TCP/IP............................... 51
B.2 USB................................ 54
C Programming 59
C.1 python example.......................... 59
D Command language 63
D.1 Wavelengthmeasurement . . . . . . . . . . . . . . . . . . . . 63
D.2PIDcontrol............................ 64
D.3Generalfunctions......................... 65
D.4Displayfunctions......................... 66
D.5 Auxilliarymeasurements. . . . . . . . . . . . . . . . . . . . . 66
D.6Imaging............................... 68
D.7 Configurationsettings . . . . . . . . . . . . . . . . . . . . . . 70
D.8EEPROMaccess......................... 73
Emogwave configuration 75
E.1 Command-lineoptions . . . . . . . . . . . . . . . . . . . . . . 75
E.2 Configurationfile......................... 77
Fmogwave server 79
F.1 Enablingtheserver. . . . . . . . . . . . . . . . . . . . . . . . 79
F.2 Communicationwiththeserver . . . . . . . . . . . . . . . . . 79
F.3 mogwave commands........................ 80

Contents v
G Ugrading firmware 83
References 84

vi Contents

1. Introduction
TheMOGLabsMWMopticalinstrumentisahighresolutiondiffractiongrat-
ingspectrometerinLittrowconfiguration. Opticalinterferencecreatesan
imageofasinglemodefibrecoreatawavelength-dependentpositionona
semiconductorimagingsensor. Theimageisdigitisedathighspatialreso-
lutionandwithhighdynamicrangeandspeed. Thewavelengthspectrumis
determinedfromthedigitisedimageandafittingproceduredeterminesthe
peakwavelength. Itprovidespicometre(0.001nm)accuracyandpicowatt
sensitivity, with up to 1250 readings per second. The relative accuracy,
forexampleinmeasuringthedifferencebetweentwolaserwavelengths,is
around10MHz(0.01pm).
The device can be operated standalone (without a host computer, see
fig.1.1)orviaawebbrowser(fig.1.2)orusingthemogwave GUIapplication
(chapter 4). Integration with data acquisition systems is straightforward
usingUSBorethernet(TCP/IP)communicationsandsimpletext-basedcom-
mands.
Figure 1.1: Wavemeteron-devicedisplay,showingserialnumber,firmwarever-
sion,wavelengthrange,temperature,pressure,exposuredurationandIPaddress.
1.1 Basic setup
1. Connect a 5V 500mA power supply via the USB interface. Some
computer USB ports will provide sufficient power but in general a
dedicatedpowersupplyorUSB hubisrecommended.
2. Second and third generation (Rev 2 and later) instruments have
1

2Chapter 1. Introduction
Figure 1.2: Webinterfacehomepage.
poweron/offviatheOKpushbutton. Topoweronoroff,holdtheOK
buttondownfor2to3seconds.
3. If possible, use a network connection for improved response times
andfasterdata acquisition. Connecttoan ethernet switchandthe
MWM willattempttodetermineanIP addressviaDHCP.Ifthatfails,
it will default to an internal IP which will be shown on the instru-
ment display. See chapter B for more information on configuring
communicationsparameters.
4. TheMWMmustbecoupledtothelightsourceviaasingle-modeopti-
calfibre. Multimodefibreisnot suitable. Theinstrumentsensitivity
isveryhighandsothefibremodediameterneednotbewellmatched;
forexample,a480nmfibrecanbeusedtomeasure780nmlightand
vice versa, though best accuracy and stability are achieved if the
fibre is matched to the wavelength. Fibres with FC/PC (preferred)
or FC/APC connectors can be used, and standard or polarisation-
maintainingfibre.
Note: Yourdevicehasbeenconfiguredandcalibratedusingafibre
witheitherFC/PC orFC/APC connector, usuallywithFC/PCatthe
wavemeter. Pleaserefertothetestdataprovidedwithyourdevice.
If you use a different connector type, you will need to reconfigure
andrecalibrate. Pleaseseesection4.8.
Caution: Thefibretipisanintegralpartoftheinstrument. Unclean

1.2 Software installation 3
ordamagedfibretipswillgiveunsatisfactoryresults.
5. The target laser should be directed into the other end of the fibre
patch cord. Note that a lens is not needed; the bare fibre will
normally couple sufficient light. A few nanowatts is good, though
whenfirstsettingup,afewmicrowattswillmakelifemucheasier.
6. The device can operate standalone, but initially it is best to use
a WindowsTM computer and the mogwave software application, as
describedinchapter4.
1.2 Software installation
The MWM can be used directly from many standard laboratory data ac-
quisition systems such as python,matlab or LabVIEW, via simple text
commands. A simple example is included in chapter C. We also pro-
vide a standalone GUI application, mogwave, which runs under Microsoft
WindowsTM.
To install the mogwave application, run the appropriate installer, for ex-
amplemogwave_setup.exe,availablefromtheMOGLabswebsite:
http://www.moglabs.com/wavemeter.html
1.2.1 USB drivers
WhenyouconnecttheMWM,yourcomputershouldautomaticallyfindand
install USB drivers from the WindowsTM update service. If not, in the
installdirectory(typicallyc:\Program Files\MOGLabs)youshouldfindthe
USB_VCPdriver folderwhichwillcontainsetupprogramsfor32-bitand64-
bitsystems.
IfyouhaveproblemsconnectingwithUSB,inparticularnodriverfound:
1. EnsurethedeviceisconnectedtoyourcomputerviaUSBcable.
2. Double-clicktheappropriate32-bitor64-bitdriverfromtheUSB_VCPdriver
folderintheinstalldirectory,typically
c:\Program Files\MOGLabs.

4Chapter 1. Introduction
3. Onceinstallationiscompleted,restartyourcomputer.
4. Whenyourcomputerisfinishedbooting,disconnecttheUSBcable
fromyourwavemeter,andthenreconnect.

2. Standalone operation
Forfullfunctionality,theMOGLabsMWMshouldbeusedwiththemogwave
WindowsTM-basedapplicationpackageprovided(seechapter4),butitcan
also be operated as a standalone instrument using the pushbuttons and
on-screenmenusystem. TheMWMalsooffersawebinterface(seechapter
3)foroperationwithawebbrowser,forexampleonasmartphone.
2.1 On-device measurements
There are currently four modes of measurement operation which can be
selectedusingthepushbuttons.
Off TheMWM iswaitingforcommandsviaethernet/USB orthewebinterface,
orforpushbuttonactivationofoneoftheothermeasurementmodes.
On The MWM measures and displays the wavelength ten times per second.
Themeasurementunitscanbeadjustedviathemenusystem(seebelow).
TheMWM automaticallyadjustsexposuretime,andusesone-dimensional
measurementofthespectralpeaklocation.
PID with display TheMWMmeasurescontinuallyatmaximumspeed,andactivates
PID control to vary the output voltage via the SMA connector to lock a
lasertoawavelengththatcanbespecifiedthroughthemenusystem. The
measuredwavelengthisdisplayedonthedeviceLCD screen.
PID no display As above, but the LCD screen shows the desired setpoint wave-
length and is not updated with the actual measured wavelength. This
allows the MWM to measure much more rapidly, at over 1250 measure-
mentspersecond.
2.2 Front panel display and buttons
The pushbuttons can be used to start on-device measurements, access
on-devicemenus,andinitiatefirmwareupgrades.
5

6Chapter 2. Standalone operation
2.2.1 Pushbuttons
There are four pushbuttons to the right of the LCD display, to select the
measurementmodeortostepthroughthemenus.
Stopmeasuring,ifdevice-basedmeasurementisactive.
Activatefirmwareupgradeifhelddownduringstartup.
↑Enable device-based measurement with on-screen display, and step up-
wardsthroughmeasurementmodes.
If held down during startup, load network configuration from hard-coded
definitionsinsteadofEEPROM.
↓Enabledevice-basedmeasurementwithon-screendisplay,andstepdown-
wardsthroughmeasurementmodes.
OK Activateon-screenmenus.
For MWM Rev 2 and later, the OK button acts as a power switch. Hold
downfor2to3secondstopoweronoroff.
OK +↓Holdbothdowntoreset.
2.3 Measuring
TheLCDdisplayimagesbelowshowthethreedifferentmeasurementmodes
in operation. On the left is the normal mode with ten measurements per
second.
ThemiddleimageiswithPID controlactivated,measuringanddisplaying
asquicklyaspossible. Thenumbershownbelowtheunits(i.e.1170/s)is
thenumberofmeasurementspersecond.

2.4 Device menus 7
The right-hand image shows the third mode of operation, where the dis-
playednumberisthesetpointratherthantheactualmeasuredwavelength.
Thatallowsslightlyfasteroperation(1250measurementspersecond).
2.4 Device menus
2.4.1 Home screen
Thedefaultscreenonpower-up,showingfirmwareversionnumber,device
serialnumber,wavelengthrange,temperature,pressure,exposuretimeand
TCP/IP orUSB connection. Pressthe OK buttontoenterthemenusystem.
2.4.2 Main menu
Mainmenu,allowingselectionofthemeasurementmodeorentryintothe
sub-menusdetailedbelow.
The ↑and ↓buttonsselectadifferentmeasurementmode(see2.1)or
Settingssub-menu. Usethe OK buttontoselectthecurrentlyhighlighted
(asinvertedtext)sub-menu. Usethe buttontoexitthemenusystem.
2.4.3 Settings
TheSettingsmenuoffersselectionofanumberofsub-menus.

8Chapter 2. Standalone operation
2.4.4 Units
TheMWM measureswavelengthinambientconditions,butusesmeasured
temperature and pressure to estimate the wavelength in vacuum, in air
at standard temperature and pressure, or asa frequency or wavenumber.
Column returnsthesensorpixelnumbercorrespondingtothespectralpeak,
fordiagnosticpurposes.
2.4.5 PID
TheMWM canoutputaPID controlsignalontheSMA connectorforlaser
wavelength stabilisation (see 4.3.4). The PID menu allows display and
adjustmentofthePID setpoint,gaincoefficients,offsetvoltageandlimits.
Thesevalueswouldnormallybeenteredusingmogwave orotherinterface
butitmaybeusefultodisplayandmakesmallchangesonthedevice.
Toalterthestaticvalues,selectthedesireditemusingtheup/downarrow
keys, then press OK. The value will be highlighted as inverted text and
can be altered using the up/down arrows. Use the button to move
the cursor to the left. The cursor cannot be moved right; instead, keep
pressing untilthecursorwrapsaround.
Press OK whenfinishededitingthevalue.
Tosavethenewvalues,movedownthemenutoSave to eeprom andpress
OK.

2.4 Device menus 9
2.4.6 Ethernet
The ethernet sub-menu shows the current IP address, and stored (static
default) values for static IP address, netmask, gateway DHCP and TCP/IP
port.
Tosaveandactivatethenewvalues,movedownthemenutoeitherSave
to eeprom orSave and restart andpress OK. BothSave optionscopythe
newvaluestoEEPROM. TheSave and restart optionwillalsoreboot the
devicewiththenewvalues.
2.4.7 Other
Rowisthesensorrowusedformeasuringwavelength. Themaximumexpo-
sure time (in milliseconds), pressure measurement correction, and screen
contrastcanalsobechanged. Notethatthereisnovaluerangechecking;
consultthecommandlanguageinappendixDformoreinformation. Alter
valuesasabove.
2.4.8 System voltages
On-boardpowersupplyvoltages,fordebuggingtechnicalproblemsincon-
sultationwithMOGLabs.

10 Chapter 2. Standalone operation
2.4.9 About
Providesinformationincludingserialnumberandfirmwareversion.

3. Web interface
With the MWM connected to your network, the device web server (see
figurebelow)providesreal-timewavelengthreadingstoanywebbrowser
includingmobilephones,desktopandlaptopcomputers. Simplyenterthe
device IP address, as shown on the LCD display (e.g. 10.1.1.128) into
your web browser and you should see a webpage similar to that below,
providedyourcomputer/phoneisonthesamesubnetastheMWMdevice.
Figure 3.1: Web interface homepage, showing the wavelength, exposure time
anddevicetemperature. Buttonsallowswitchingtoreal-timewavelengthdisplay,
auto-adjustofexposuretime,enablingPID,andjumpingtoadevicesetuppage.
Web page common features
Alldevicewebpageshavesomecommonelements:
•Thedevicefirmwareversion,IPaddressandIPportnumberareshown
atthetoprightofeachpage.11

12 Chapter 3. Web interface
•TheMOGLabslogocanbeclickedtoaccesstheMOGLabswebsite.
•The menu bar provides access to several key Functions, the device
Homepage,andtoaHelppagewhichprovidesalinktothisuser-
manualviatheMOGLabswebsite.
3.1 Home page
Thehomepageshowsasinglewavelengthreading(inthedevicedefault
units), the exposure time, the device temperature, the status of the PID
servo(onoroff),andseveralclickablebuttons.
Update Updatesthedisplayedwavelength,exposure,temperatureandPID status.
Live Linkstoanewwebpagewithlivedisplay(seebelow).
Live+ Linkstoanewwebpagewithlivedisplayofjustthewavelength,inlarge
font. Particularlyusefulforuseonsmallscreenssuchassmartphones,or
toviewthereadoutfromacrossthelab.
Auto exposure Recalculatestheoptimumexposuretime.
Device setup Linkstoanewwebpageforconfiguringthedevice;seebelow.
PID off/on TogglesPID statusbetweenonandoff.