Writing a Coordinate File
=========================

Structures on chip are defined by the 2 dimensional coordinates of the IO ports, no matter whether the ports are electrical or optical.

Each structure must be listed on the coordinates files a basic entry would be:

.. parsed-literal::
        ## Structure Name
        BSplit3
        #OW
        1.850477 1.513309
        #OE
        1.765477 1.19150
        ##

Each structure must be confined within a set of two ``##``. The Structure Name will be used to in ``ProberControl`` to refer to this structure. To define the stage for an optical stages oriented in the West a first line ``#OW`` is followed by the coordinates x and y. An electrical stage on the north would be defined as ``#EN``, etc. Although internally the ProberControl has dedicated coordinate systems for each stage (see figure) the coordinates file always refers to the chip coordinate system which is the same as a south oriented stage.

.. image:: ..\..\_static\coordinatePlanes.PNG
    :width: 225px
    :align: center
    :height: 250px

Note that the y axis is reversed compared to an intuitive coordinate system.

Coordinates for fiber arrays or multi-channel probes should always reference the left-most (when looking along the device) channel of the device:

.. image:: ..\..\_static\multiChannelCoordinate.png
    :width: 437px
    :align: center
    :height: 236px


When a structure is connected the system will try to fine align the optical probes using a feedback loop. The feedback loop in and outputs are defined as follows:

.. parsed-literal::
        #FeedbackIn
        Current:0.001,EN:1
        #FeedbackOut
        Power,OW:8
        #Continuous
        True

In this example a DC Source is used to source 1 mA of current into port 1 of the electrical probe in the north. The signal is picked up on the optical probe in the west on fiber 8 and the measured power is used as a the feedback signal. The #Continous True makes the system continously optimize its position as apposed to optimize only once.

Options for the input are:

.. parsed-literal::
        #FeedbackIn
        Current:0.001,EN:1
        #FeedbackIn
        Power:1550,OW:1

where the second options defines a laser light at a 1550 nm wavelength supplied at optical probe in the west on fiber 1.

Options for the output are:

.. parsed-literal::
        #FeedbackOut
        Power,OW:8
        #FeedbackOut
        Current,ES:2