IPM5300 Features

• In-line Fiber-Based Polarimeter
• Wavelength Range: 1510 - 1640 nm
• Insertion Loss: <1.1 dB
• Dynamic Range: 45 dB (-30 dBm to 15 dBm)
• High Sampling Rate: 1 Million Samples per Second
• Excellent Accuracy: ±0.25° on Poincaré Sphere

Introduction
The IPM5300 is a fiber optic polarimeter that enables high speed measurements of the State of Polarization (SOP). The in-line fiber design provides an insertion loss of less than 1.1 dB, a dynamic range of 45 dB, and an accuracy of ±0.25° on the Poincaré Sphere with a sampling rate of 1million complete SOP measurements per second. The all fiber polarimeter is based on patented Fiber Bragg Grating (FBG) Technology. Its novel combination of in-line polarimetric measurement, low insertion loss, high speed, and accuracy enables unprecedented measurement of the state of polarization in fiber optical applications. For more information, please see the Operation tab.

IPM5300 Applications

• State of Polarization Measurements at 1 Million Samples per second
• High Speed DOP Measurements for Active Polarization Mode Dispersion Compensation
• High Speed Feedback for Automatic Polarization Control

Operation Mode
All four Stokes values, which fully characterize a SOP, are provided either as analog output voltages or as digital values to the PC. The SOP measurement can be controlled via an external trigger function allowing the synchronization of the IPM5300 with other devices. The update rate of 1 MHz applies to the fully characterized SOP measurement.

Modular Design
The IPM5300 is based on the Thorlabs TXP5000 Modular Test & Measurement System and is controlled by a PC via easy to use graphical user interfaces (see User Interface tab). It offers additional features like USB/Ethernet ports, plug and play combination with other modules, and flexible configuration via LabVIEW™, LabWindows/ CVI™, MSVC and Borland C drivers.

2 Versions To Choose From

• Benchtop Version including PC: IPM5300-T
• Module Version for TXP chassis: IPM5300

Figure 1

How it Works

The IPM5300 polarimeter is an in-line polarimeter that utilizes custom Fiber Bragg Gratings (FBGs). See Figure 1 for a diagram of the optical schematic of the polarimeter module. The device uses two pairs of FBGs whose reflectivity is polarization dependent, to direct very small percentages of the transmitted optical power to four detectors. A λ/4 fiber waveplate is positioned between the two pairs of FBG's to produce the two additional elliptical states of polarization.They are required for a full analysis of an arbitrary state of polarization. TheIPM5300 overcomes the limitations of other fiber based in-line polarimeter designs by eliminating the need to use tap couplers which show significant temperature and wavelength sensitivity. The FBG approach offers superior performance; it provides an extremely broad wavelength range (1200nm-1700nm) as well as highly accurate SOP and DOP measurements.

Operation Mode
Thorlabs IPM5300 in-line polarimeter measures the four stokes parameters of the signal to determine the State of Polarization (SOP). The resulting SOP can then be presented either on the Poincaré Sphere, the Polarization Ellipse or in time domain (See User Interface tab). The IPM5300 can be activated in two modes: single mode or array mode.

Single Mode
In this mode the polarimeter measures one state of polarization after another. There is no defined time scale. If one measurement has finished and the data is transferred to the PC, the next measurement starts. The results can be taken from the analog output or can be displayed through the GUI.
This mode should be used when there is no fast polarization change that can be observed by the user.

Array Mode
In this mode sample rate and the number of measurement points (max. 1024) are predetermined. The complete measurement results are transferred to the PC after all n points are measured. This allows having a defined time scale for the measurement as well as a hardware trigger and the registration of pre-trigger samples. The data can then be displayed graphically or numerically on the GUI. This mode is ideal when fast SOP changes occur (see Application tab for a specific example). The measurement results can be saved in an ASCII file.

Fiber Connection
The standard fiber connection for input and output is FC/APC, however, other connections are available upon request. The SOP at the output is different from the measured SOP since there is a single mode fiber between the actual in-line polarimeter and the output port. This fiber will transform the polarization.

Graphical User Interface

The in-line polarimeter IPM5300 measures the State of Polarization (SOP), the Degree of Polarization (DOP) as well as the signal's power. The graphical user interface can present the data in one of the following graphical interfaces: a Poincaré Sphere, a Polarization Ellipse or on a time domain chart. Additionally, the data can also be displayed numerically.

Poincaré Sphere

The Poincaré Sphere window shows you the actual status of the output polarization on the transparent sphere and also shows numerically the three stokes parameters s1, s2 and s3. To distinguish between two opposite modes the Polarization states on the front side of the transparent sphere are shown in red, on the rear side in blue. The user interface allows rotating and zooming into the Poincaré sphere.

Polarization Sphere

Another representation of the polarization status is shown as polarization ellipse, with numerical values for the Ellipticity and Azimuth angle. 'R' or 'L' are shown on the display for right- and left-handed polarization.

Time Domain Chart Mode

In the Chart mode the user can view the stokes parameters versus time and can control and adjust the measurement parameters such as samples and averaging time.

Example of the Measurement Capability

This example shows that the IPM5300 precisely and accurately measures fast changes of the States of Polarization (SOP).

An example of the measurement capability of the IPM5300 polarimeter is demonstrated in the data shown below. A system, shown above, was set up to demonstrate the capabilities of the IPM5300. A fiber pigtailed laser was used as the input to the polarization controller. The signal from the controller was fed to the IPM5300 that was installed in a TXP chassis, which was controlled via a local computer. The acquired data included the state of polarization (SOP), the change in SOP, the power and DOP. This data is shown in Figures 1 and 2. The polarization controller (e.g. Thorlabs DPC5500), a piezoelectric based controller, was controlled with a square wave signal at 2kHz to cause quick changes in the state of polarization into the polarimeter. The induced polarization change was 82° on the Poincaré sphere.

Figure 1a shows the measured Stokes vector elements (S1, S2 and S3), while Figure 1b shows the angular deviation in the state of polarization on the Poincaré sphere. Figure 2 shows the total measured power and the DOP versus time. One aspect of the data that is clearly evident in Figure 1 is the ripple. The polarimeter, at 1 million samples per second, accurately measures the SOP as the controller changes polarization (Figure 1a). The ripple in the data has a period of 20µsec (50kHz), which is easily resolved by the polarimeter. This ripple is real variations in SOP caused by effects of variations in the mechanical stress on the fiber due to a 50kHz mechanical resonance in the piezo controller. Despite the resonance, the measured optical power and DOP was constant as the polarization was changed. The deviations in the data are at the measurement uncertainties of the polarimeter, < 0.02 dB and < 0.1% respectively.

The following data was taken using a standard piezoelectric polarization controller to change the input SOP to the IPM5300 from one state to another. The ripple in the data is due to mechanical resonance in the piezo elements.

Figure 1

a) Measured s1, s2 and s3 versus time as the input SOP is changed from one state to another

b) The deviation in SOP versus time as the polarization is changed from one state to another. This shows ~82° deviation on the Poincaré sphere.

The data below was captured simultaneously with the data in the plots above.

Figure 2

a) Measured optical power (dBm) versus time as the input SOP is changed from one state to another via a standard piezoelectric polarization controller.

b) The DOP versus time as the polarization is changed from one state to another. This shows ~82° deviation on the Poincaré sphere.

Auxiliary Connection

D-Type Female

The Software Package for the TXP5000 Platform contains the Software Modules for the IPM5300

Use this link to download the following software packages:

The available software is organized into the following categories:

1. Applications: Standard application software packages and graphical user interfaces. This is what most users need to operate the device for typical applications.
2. Drivers: Instrument drivers for the National Instruments™, LabWindows™/CVI, and LabVIEW™ development environments. These are intended for developers who want to extend or adapt the functionality of the device to their special requirements.
3. Firmware: Low level software for the internal operation of the device. This should be updated to the newest version available to guarantee optimal performance. Please see the Operating Manual for information on how to update the firmware of your device.