In optical interconnection technology, high-speed and large data transitions with low error rate and cost reduction are key issues for the upcoming 8K media era. The researchers present notable types of optical manufacturing structures of a four-channel parallel optical module by fully passive alignment, which are able to reduce manufacturing time and cost. Each of the components, such as vertical-cavity surface laser/positive-intrinsic negative-photodiode array, microlens array, fiber array, and receiver (RX)/transmitter (TX) integrated circuit, is integrated successfully using flip-chip bonding, die bonding, and passive alignment with a microscope. Clear eye diagrams are obtained by 25.78-Gb/s (for TX) and 25.7-Gb/s (for RX) nonreturn-to-zero signals of pseudorandom binary sequence with a pattern length of 231 to 1. The measured responsivity and minimum sensitivity of the RX are about 0.5 A/W and ≤−6.5 dBm at a bit error rate (BER) of 10−12, respectively. The optical power margin at a BER of 10−12 is 7.5 dB, and cross talk by the adjacent channel is ≤1 dB.
We present an advanced demodulation technique for a fiber-optics interferometric current transducer. A quadrature sampling method with internal triggers was adopted for structural simplification and cost-effective phase demodulation. The internal triggers for quadrature signal processing were generated at zero crossing points of an ac-coupled reference signal, which was distinguished from the current-induced interference signal by utilizing fiber Bragg grating. Phase variation was extracted from the arctangent demodulation process. The proposed technique demonstrated accurate and stable phase demodulations performance and better than that of the conventional lock-in amp demodulation.