BIDI Test Board User s Guide

Transcription

1 Tx disable Driver IC BIDI Tx data Signal detect Rx data Post Amp Features Laser driver and post amplifier mounted on board Data rate up to 2.5 Gbit/s Separate power supplies for Tx and Rx Adjustment of laser bias and modulation currents with potentiometers Operation at 3.3V or 5.0V Lars Leininger 1

2 1. Overview 2 2. Measurement set-up 3 3. Laser BIAS and MOD setting 5 4. Tx disable input 6 5. SD level adjustment 6 6. Examples for measurement results 6 7. Revision History 7 8. Contact information 7 1. Overview This test board is designed to evaluate the performance of the Infineon BIDI modules. Supported are all BIDI modules with pinning #2 for the transmitter and with incorporated TIA at the receiver. The power supplies for Tx and Rx are completely separated on the board layout. BIDI pinning #2: Pigtail Transmitter Receiver with preamp 1 LD Cathode 1 Out Gnd, Case 2 Gnd, Case 3 LD anode / monitor diode cathode 3 Out Monitor diode anode 4 Vcc Transmitter Receiver Lars Leininger 2

3 Inputs: Label on test board Description Setting Min Typ Max Tx Vcc Vcc driver IC 3.1 V 5.2 V Tx Vee Vee driver IC 0 V Rx Vcc Vcc postamp IC and BIDI TIA Vcc=5.0V Vcc=3.3V 3.1 V 4.8 V 3.3 V 5.0 V 3.5 V 5.2 V Rx Vee Vee postamp IC and BIDI TIA 0 V Tx DAT+ Differential data input Tx P Tx DAT- Tx GND solder pad Rx GND solder pad Differential data input Tx N Ground, can be used to additionally ground the BIDI housing to improve sensitivity (only use one of both, otherwise Tx GND and Rx GND will be connected). For, Tx and Rx GND are connected. Outputs: Label on test board Description Output Min Typ Max SD Signal detect Rx 2.4 V Rx DAT+ Differential data output Rx P Rx DAT- Differential data output Rx N 2. Measurement set-up Attach the BIDI to the test board and solder the pins to the pads: LDC: Laser Diode Cathode LDA/MDC: Laser Diode Anode, Monitor Diode Cathode Not marked (middle trace): Tx: Monitor Diode Anode (pin #4) Rx: Vcc (pin #4) The pins do not have to be shortened to get good performance at high data rates. Soldering the leads near to the BIDI housing reduces the influence of the pin inductance. The ground pins #2 for the Tx, Rx are connected to the lower side of the test board. Preadjust the bias current with potentiometer R1 (BIAS) according to chapter 3. The resistance can be measured with a multimeter on pads TP5, TP6 with the power supply switched off. The laser can be damaged if the bias current setting is too high! Connect the power supply for the Tx and Rx circuitry. The voltage setting for the Rx depends on the TIA used in the BIDI (3.3V or 5V version). Never operate a 3.3V TIA with 5V! The driver IC and receiver IC operate with both voltages. Connect the differential data inputs Tx DAT+ and Tx- to a pattern generator. Settings: Lars Leininger 3

4 Data input signal specification Min Max Tx DAT input voltage low Vcc=3.3V Vcc=5.0V 1.0 V 2.2 V Tx DAT input voltage high Vcc=3.3V Vcc=5.0V 3.3 V 5.0 V Data input swing 250 mv 1600 mv If you use a pattern generator a typical voltage setting is Amplitude 400 mv, Offset=0V. Adjust the modulation current with potentiometer R2 (MOD). Switch on the power supply for the Tx, view the laser output on the oscilloscope. To detect the Rx output connects Rx DAT+ or Rx DAT- to the input of the oscilloscope. Terminate the unused data output with a 50-Ohm resistor or connect the output to a BERT. Data output signal specification Min Max Rx DAT output voltage low Vcc-1.8V Vcc-1.3V Rx DAT output voltage high Vcc-1.1V Vcc-0.65V Data output swing 500 mv 1000 mv The following chip currents are typically measured at the power supplies for the Tx and Rx circuits. In the case for the Tx, the current depends on the settings of laser bias current and modulation. Measurements were performed with BIDIs SBH52464N (1310nm high power) and SBL92354N (low power 1550 nm). Chip currents Vcc, V I, ma Tx, laser off Tx, laser on Rx, no input signal Rx, signal received Lars Leininger 4

5 3. Laser BIAS and MOD setting The bias controller integrated in the driver chip controls the laser diode output power by adjusting the bias current. The voltage at TP5 represents the controller feedback input. The voltage level depends on the monitor diode current and therefore on the laser output power. MDC MDA to chip Monitor Diode R30 100R TP5 TP6 Tx GND The bias current is adjusted with the potentiometer R1 (BIAS) between points TP5 and TP6. It is important that R1 is preadjusted properly before powering up the board with a new BIDI to prevent a high bias current, which may damage the laser. R1 should be set to 12 kohms when a new BIDI is used. The laser can be damaged if the bias current setting is too high! Measurements performed with BIDIs SBH52464N (1310nm high power) and SBL92354N (low power 1550 nm): BIAS setting optical average power, uw SBH52464 SBL92354 R bias, kohm The settings of R1 (BIAS) and R2 (MOD) depend on the laser threshold, the laser differential efficiency and the monitor diode response. Therefore the bias and modulation has to be adjusted for each device. The optimum settings for 2 BIDIs are listed below as an example: BIDI R1 (BIAS) KOhm Opt. Average power, mw R2 (MOD) KOhm SBH52464N SBL92354N Lars Leininger 5

6 Clockwise rotation of the potentiometer screw decreases the resistance and increases the bias/modulation currents. The values for R1, R2 on the test points TP3, TP4 and TP5, TP6 have to be measured with the power supply switched off. 4. Tx disable input The Tx disable input could be used by soldering a SMA connector to the pad marked as Tx DISABLE. The component is a Johnson Components SMA End Launch connector, P/N A low level input enables, a high level disables the laser diode. The boards are delivered with the input tied to Vee. The wire connecting the disable input and Vee has to be removed to enable the functionality. Input voltage high is 2V..Vcc, input voltage low is V. 5. SD level adjustment The function SD is currently not implemented and cannot be used. 6. Examples for measurement results BIDI SBH52564N, optical output Tx, pattern PRBS 10(15) Mbit/s, unfiltered 1250 Mbit/s, unfiltered 2500 Mbit/s, filtered, OC-48 mask Lars Leininger 6

7 BIDI SBL92354N, optical output Tx, pattern PRBS 10(15) Mbit/s, unfiltered 1250 Mbit/s, unfiltered 2500 Mbit/s, filtered BIDI SBH52564N, electrical output Rx, pattern PRBS 10(15) Mbit/s 7. Revision History Testboard S23481-A is available. Tx and Rx circuitry have separate ground planes. Label on board: A Testboard is available. Tx and Rx circuitry have a common ground plane to reduce cross talk between Tx and Rx. Label on board: A5159-A1 8. Contact information Lars Leininger Application Manager Fiber Optics INFINEON Technologies of North America 1730 North First Street, M/S San Jose, CA95112 Phone (408) lars.leininger@infineon.com Lars Leininger 7