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ONET-10G-EVM Question

Other Parts Discussed in Thread: ONET1151L, ONET1151P

Hello Team,

Customer mentioned they received documentation on the ONET-10G-EVM but not clear on the questions that follow:

-How to control the voltage that is passed through a laser?

- Is there a guide for “how to connect” or “how to start”?

Will appreciate your help with these questions.

Thanks,

Mizanur

Central Apps team, EMEA

  • Hello Team,
    Can we expect an answer to the questions?
    Customer is waiting for 2 weeks now.
    Thanks,
    Mizanur
  • Hi Mizanur,

    The Userguide includes an overview of the Setup instructions for the Reference design board, in Section 3.

    The peak-to-peak modulation current that drives the TOSA is configured through the internal registers 2 and 3 of the ONET1151L device on the module board. Using the Host board GUI, it can be controlled in two ways: 1) By Selecting "Device Configuration" for the ONET1151L for high-level GUI control of the device; OR 2) By using the "Low Level Register Interface" to directly program the registers. Figure 11 in the Userguide shows the GUI with the Modulation Current adjustment control knob pointed out. Note that the Modulation current can be set to as high as 85mA, depending on the desired Extinction Ratio from the TOSA.

    Here's the step-by-step instructions on how to configure the module using the Host board:

    Quick Set-Up Instructions:

    1. Run the GUI software executable file provided on the CD and follow the installation instructions.
    2. Plug the SFP+ module into the SFP+ connector on the host board.
    3. Connect a differential data-input signal source to the transmitter SMA connectors TDP/TDN. Set the
    data rate up to 11.3-Gbps and set the amplitude between 150-mVp-p differential and 1200-mVp-p
    differential.
    4. Connect the receiver differential outputs RDP/RDN to the input of an oscilloscope.
    5. Connect the TOSA output to the input of an oscilloscope.
    6. Connect an optical source to the ROSA input.
    7. Apply a 3.3-V supply to the 3.3-V banana jack and the supply ground to the GND banana jack (P1 and
    P2). The typical current consumption is about 122 mA.
    8. Attach the interface cable from the USB port of the computer to the USB port on the host board. LEDs
    D1 and D4 light up green.
    9. Set the TX_Disable switch (S1) to LOW.
    10. Run the GUI by clicking on the desktop icon. Ensure that the EVM is powered on before the GUI is
    started.
    11. Select Device Configuration for the ONET1151L or ONET1151P for high-level GUI control of each
    device. Alternatively, the Low Level Register Interface can be used to directly program the registers.
    12. The ONET1151P powers up in default mode with all registers set to zero except for the the output
    amplitude register (Reg3) which is set to 0x02.
    13. The ONET1151L powers up in a disabled state (Chip Enable = 0). To enable the device, click on Chip
    Enable.
    14. For initial evaluation, open-loop operation is recommended. Select Open Loop and adjust the bias
    current to set the average optical power. Adjust the modulation current to set the extinction ratio.
    15. The transmitter performance can be optimized by adjusting the de-emphasis, back termination
    resistance and the limiter stage bias currents.

    Please let me know for further questions.

    Thanks,

    Sri

  • Hello Sri,

    Many thanks for your reply.

    Customer came back and says that it is not clear how to control the voltage that is passed through a laser:

    "It is not still clear: How to control the voltage that is passed through a laser?”

    Is this a valid question? I mean, does the laser pass voltage through it?

    Best regards,

    Mizanur

    Central Apps, EMEA

  • Hi Mizanur,

    The laser used in the reference design is a Directly-modulated laser (DML), which is driven by current modulator, not voltage modulator. The ONET1151L which is the DML-driver in this module, provides the current modulation that drives the laser, along with a bias current input to it. The laser then outputs optical signal that follows the modulation current signal.

    This modulation current can be configured through the internal registers 2 and 3 of the ONET1151L device on the module board. Using the Host board GUI, it can be controlled in two ways: 1) By Selecting "Device Configuration" for the ONET1151L for high-level GUI control of the device; OR 2) By using the "Low Level Register Interface" to directly program the registers. Figure 11 in the Userguide shows the GUI with the Modulation Current adjustment control knob pointed out.

    Thanks,
    Sri
  • Hello Sri,
    Thanks for the further clarification.

    Best regards,
    Mizanur