FFP-C Fiber Fabry-Perot Controller OPERATING INSTRUCTIONS Version 1.0 MICRON OPTICS, INC. 1852 Century Place NE Atlanta, GA 30345 USA Tel (404) 325-0005 Fax (404) 325-4082 www.micronoptics.com
Page 2 Table of Contents Section Page # 1.0 Features 1 2.0 Description 1 3.0 Panel Layout 2 4.0 Set-up 3 5.0 Typical Configuration 4 6.0 Operation 5 7.0 Troubleshooting 5 8.0 Specifications 6 9.0 Supply Voltage Selection 7 10.0 Block Diagram and Circuit Schematic 8 Acronyms DBR DFB ECL FC/PC FC/SPC FFP FFP-C FFP-SI FFP-TF FSR PZT Distributed Bragg Reflector Distributed Feedback External Cavity Laser FC connector with physical contact polish FC connector with super physical contact polish Fiber Fabry-Perot Fiber Fabry-Perot Controller Fiber Fabry-Perot Scanning Interferometer Fiber Fabry-Perot Tunable Filter Free Spectral Range Piezoelectric Transducer
Page 3 1.0 Features Controls either the FFP-TF or the FFP-SI Scan mode o Supplies a triangle wave to the FFP device which allows tuning over more than 50 volts o Adjustments for peak-to-peak amplitude, frequency and offset Dither mode o Supplies a 2 KHz dither frequency to the FFP devices for feedback loop o Automatic gain control provides greater than 40 db dynamic range o Wavelength locked tracking range greater than 50 volts Built-in photodetector with FCPC input Auxiliary Electrical Input Digital voltmeter for PZT control Rear BNC outputs for oscilloscope 2.0 Description The Micron Optics, Inc. (MOI) FFP-C is an electronic piezoelectric actuator driver and optical signal processor especially designed for the FFP series of optical devices. This unit allows tunable filters and scanning interferometers to be used in all modes of operation: A manual wavelength selection mode tunable over more than 50 volts or typically 4 FSRs. A wavelength scanning mode adjustable over more than 50 volts or typically 4 FSRs. A closed-loop mode for wavelength locking the FFP-TF or FFP-SI to a narrow-line wavelength source and remaining locked over the entire voltage range. The FFP series of filters and interferometers has excellent thermal and long-term stability; however, wavelength locking is required to achieve optimum stability. The FFP-C in closed-loop operation compensates for mechanical, thermal, or other wavelength variations in the FFP-TF or FFP-SI, and the input source. NOTE: The FFP-C is intended for laboratory demonstrations of FFP filter characteristics and general modes of operation. It is not intended for field applications.
Page 4 3.0 Panel Layout 3.1 Front Panel Item # Name Description 1 Auxiliary Input Secondary input (electrical), used only in special applications when primary input is not used, SMA connector 2 Optical Input Primary input (optical), FC/SPC connector 3 Scan/Dither switch Switch between scan and dither modes 4 Lock/Unlock switch Switch between lock and unlock modes, only operates when in dither mode. 5 Scan Amplitude control Controls peak-to-peak scan amplitude 6 Scan Frequency control Controls scan frequency 7 Offset control In scan mode controls scan offset, in dither/unlock mode controls DC offset, disconnected in dither/lock mode 8 Output Meter Displays the DC level of the voltage supplied to FFP device, mainly used in dither mode or in scan mode when scan amplitude is small. Also indicates power is ON when illuminated. 9 Output to FFP Electrical connection to FFP device
Page 5 3.2 Rear Panel Item # Name Description 10 Test Output Output to monitor optical signal with an oscilloscope, BNC connector 11 Sync Output Output to trigger oscilloscope sweep, BNC connector 12 PZT Output Output to monitor PZT voltage supplied to the FFP device with an oscilloscope, BNC connector 13 Power On/Off switch Power switch on (l) or off (O) 14 Power Cord connection AC power cord connection 15 Supply Voltage selection Select 95-135 VAC or 190-265 VAC, fuse holder 4.0 Set-up 4.1 Included with the FFP-C is an FFP cable used to connect controller output to the FFP device. Also included is an AC power cord. Check that these are included. For compliance with the immunity standard, EN6100-4-4 and 6, cables connected to the FFP-C should not exceed 3 meters in length. 4.2 Verify that the indicated voltage on the Supply Voltage selection (15) is correct for local AC power. If the indicated voltage is not correct see Section 9.0, Supply Voltage Selection. 4.3 Turn SCAN AMPLITUDE (5) and SCAN FREQUENCY (6) fully counter-clockwise. 4.4 Plug power cord to FFP-C and to AC power outlet. 4.5 Switch FFP-C power to ON (13). Scan indicator and Output meter should illuminate. Allow 2 minutes warm-up time. 4.6 Connect FFP cable to the FFP-C and the FFP device making sure the red lead is connected to positive (+) terminal and the black lead is connected to negative (-) terminal. To remove the FFP cable from the controller, slightly lift the connector while gently pulling. WARNING: Reversing the FFP voltage can cause permanent damage to the FFP device!
Page 6 5.0 Typical Configuration A typical configuration for monitoring FFP input voltages and FFP optical output with a standard oscilloscope is described below. 5.1 Connect oscilloscope channel 1 to PZT (BNC 12) on rear panel. Set channel 1 sensitivity to 5 or 10 volts/div. 5.2 Connect oscilloscope channel 2 to TEST (BNC 10) on rear panel. Set channel 2 sensitivity to ~ 0.1 volts/div. Adjust sensitivity as necessary. NOTE: The TEST OUTPUT cannot be used to monitor the AUX INPUT; therefore, the AUX signal must be connected to channel 2 of the oscilloscope with a separate cable. 5.3 Connect oscilloscope external trigger to SYNC (BNC 11) on rear panel. Set slope to +, source to external, and sweep to 1 msec/div. 5.4 If FFP device is not already connected to controller, follow instructions in Section 4.0, Set-up. 5.5 Typical optical connections using the optical input and a FFP device are shown below. 5.6 If the AUX INPUT (1) is used, take care that specifications in Section 8.9 are not exceeded. NOTE: Either the AUX INPUT (1) or OPTICAL INPUT (2) may be used separately, never at the same time.
Page 7 6.0 Operation 6.1 Scan Mode 6.1.1 Check that the SCAN indicator is lit, if not, push SCAN/DITHER switch (3). 6.1.2 Adjust OFFSET (7) to approximately 30 Volts, the middle of the controller supply voltage range. 6.1.3 Adjust SCAN FREQUENCY (6) and SCAN AMPLITUDE (5) to give one positive going ramp over the width of the oscilloscope display and the desire peak-to-peak voltage. 6.2 Dither (Lock) Mode 6.2.1 Check that the DITHER indicator is lit, if not, push SCAN/DITHER switch (3). 6.2.2 Adjust OFFSET (7) so that the desired wavelength is transmitted through the FFP device. 6.2.3 Push LOCK/UNLOCK switch (4). Lock indicator will illuminate when the controller is in the lock mode. If the FFP device is locked a stable positive voltage with a low amplitude 2nd harmonic of the dither frequency will be displayed on the oscilloscope. 7.0 Troubleshooting OPTICAL SIGNAL POWER FLUCTUATES This is typically caused by the formation of an external cavity, either before or after the FFP device and can be tested by simply wiggling the input or output fiber. If the power fluctuates when either fiber is wiggled, then an external reflection is combining with the FFP device to form a secondary cavity. External reflections can originate from splices, connectors, detectors and other optical components. A small insertion loss of 0.5 db or greater within the external cavity will usually eliminate optical power fluctuations; however, in some applications an isolator may be required. Many laser are extremely sensitive to incoming reflections (ECL, DBR, DFB, etc.) and an isolator is almost always required in front of the FFP device when used with these components. Cannot Lock the FFP Device Check that the optical input to the controller is within the specifications (Section 8.8). Check that the optical signal linewidth is several times narrower than the FFP bandwidth. Check that the optical signal noise is at least 3 db lower than the optical signal. If other wavelengths peaks are present, check that the FFP device is properly tuned to the correct wavelength (Section 6.2.2) before the Lock/Unlock is operated (Section 6.2.3).
Page 8 8.0 Specifications 8.1 Power Supply 95-135 VAC or 190-265 VAC, 15W 8.2 DC Offset Tuning Range from < 5 to > 55 Volts 8.3 Ramp Frequency 20-100 Hz Amplitude 0-55 V 8.4 Dither Frequency 2.0 khz + 20% Amplitude 8-12 mv 8.5 PZT BNC Output Impedance R 10 kω Output Level -28 to 28 V (Corresponding to 5-59.0 V PZT Output) 8.6 SYNC BNC Frequency Scan/Dither Frequency Output Voltage V (low) 0 V, V(High) 12 V Output Impedance R(5 kω) C (100 pf) 8.7 TEST BNC Output Impedance R 10 kω Output Voltage 0 to 12 V 8.8 Optical Input Input Optical Power Modulation Frequency of Input Optical Signal 8.9 Electrical Input Input Impedance Maximum DC Voltage Dither Signal Amplitude Dither Signal Phase Delay -50 to -10 dbm, unless otherwise specified dc ~ 100 khz (Optical signals with higher modulation frequencies, use AUX input) R 10 kω 12 V 10 µv to 80 mv ϕ < 20 o referenced to PZT BNC output
Page 9 9.0 Supply Voltage Selection To change supply voltage selection from current setting: 9.1 Open cover using small blade screwdriver or similar tool. 9.2 Remove voltage selector card and rotate card so that desire voltage is pointing toward the controller. Position indicator pin into groove opposite desired voltage as shown. Replace selector card and replace cover.
Page 10 10.0 Block Diagram and Circuit Schematic Optical Receiver Dither Signal Pre-Amplifier AGC Amplifier Phase Detector Test BNC Ramp Generator Dither Generator Integrator Automatic Biasing Sync BNC Scan/Dither Lock/Unlock Digital Voltmeter Power Amplifier PZT BNC FFP -30V
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