4.2 Open-Loop Operation Without Fault Detection or Digital Monitoring

With the USB2ANY GUI, write the register settings as shown in the following steps. After each write sequence, perform a read operation to make sure the change has gone into effect

NOTE

TI recommends to initially operate the TOSA in open-loop mode, with fault detection disabled, and enable the Laser Bias Current: Reg 0x01 = 0x14.

1. Set TX Output Mode to Single Ended Mode (OUTP): Reg 0x0D = 0x40
2. Set the desired TX Laser Bias Current: For example, in setup for Figure 10 we have Reg 0x0F = 0x60
3. Set the desired Transmitter Modulation Current: Reg 0x0C = 0x050
4. Use Reg 0x0E to adjust the cross point. For this setup, use reg 0x0E = 0xAF

NOTE

If the transmitter modulation current is less than approximately 0xC0, TI recommends that the designer use the slow edge speed mode (Reg 0x0D[4] = 1'b}. The need for this mode, however, is TOSA-dependent.

5. Disable and bypass the TX-CDR for ONET1130EP evaluation: Reg 0x0A = 0x10
6. Set the Desired RX Output Amplitude: Reg 0x08[3:0]
7. Set the Desired De-Emphasis: Reg 0x08[6:5] = 10'b
8. Disable and bypass the RX-CDR for ONET1130EP evaluation: Reg 0x04 = 0x18
Figure 11. 10.3125-GBps Open-Loop RX Eye Diagram