By using only two input signals of A and B, an all-optical half adder that utilizes a cross gain modulation in
semiconductor optical amplifiers is demonstrated at 10 Gbps. The half adder utilizes two logic functions of SUM
and CARRY, which can be demonstrated by using the XOR gate and the AND gate, respectively. The extinction
ratios of SUM and CARRY are approximately 6.1 dB. No additional input beam such as clock signal or
continuous wave light, which is required in many other all-optical logic gates, is used in this design concept.
Using the cross-gain modulation (XGM) characteristics of semiconductor optical amplifiers (SOAs), multi-functional
all-optical logic gates including XOR, AND, and OR gates are successfully demonstrated at 10 Gbps by using VPI
component makerTM simulation tool. Multi-quantum well (MQW) SOA is used for the simulation of all-optical logic
system. Our suggested system is composed of four MQW SOAs, SOA-1 and SOA-2 for XOR logic operation and SOA-
3 and SOA-4 for AND logic operation. By the addition of two output signals XOR and AND, all-optical OR logic can
be obtained.
KEYWORDS: Logic, Semiconductor optical amplifiers, Modulation, Logic devices, Clocks, Electrons, Signal processing, Optical signal processing, Signal generators, Computing systems
By using cross gain modulation in semiconductor optical amplifiers, basic logics for all-optical computing
and signal processing are successfully demonstrated at 10Gbps. These functions will bring up the increased
speed and capacity of telecommunication systems, basic or complex optical computing, and many other optical
signal processing systems.
An all-optical full adder using semiconductor optical amplifiers has been demonstrated at 10 Gbps for the first time. The full adder consisted of XOR and NOR gates only utilizes the mechanism of cross-gain modulation. The full adder utilize two logic functions of SUM and CARRY, which can be demonstrated by using two XOR gates and four NOR gates, respectively. By passing signal A as probe signal and signal B as pump signal into SOA-1, Boolean A NOT B can be obtained. Also, by changing the role of signals A and B for SOA-2, Boolean NOT A B can be acquired. Addition of Boolean A NOT B and NOT A B results in NOT A B + A NOT B , which is Boolean expression of logic XOR. By passing this XOR signal and signal C into the second XOR gate with the same principle, SUM signal of the full adder can be obtained. The Boolean expression of SUM can be expressed as A # B # C . With the first three NOR gates, Boolean NOT(A+B), NOT(B+C), and NOT(C+A) can be obtained. With the addition of these outputs, Boolean NOT(A+B) + NOT(B+C) + NOT(C+A) can be formed. By injecting these outputs through the last NOR gate with clock signal, CARRY signal of the full adder can be realized. The Boolean expression of CARRY can be expressed as AB +BC +CA. The extinction ratio is about 6.1dB.
By using gain nonlinearity characteristics of semiconductor optical amplifier, an all-optical binary half adder at 10 Gbps is demonstrated. The half adder operates in single mechanism, which is XGM. The half adder utilizes two logic functions of SUM and CARRY, which can be demonstrated by using the XOR gate and the AND gate, respectively. In the XOR (A NOT B + NOT A B) gate, Boolean A NOT B is obtained by using signal A as a probe beam and signal B as a pump beam in SOA-1. Also, Boolean NOT A B is obtained by using signal B as a probe beam and signal A as a pump beam in SOA-2. By adding two outputs from SOA-1 and SOA-2, Boolean A NOT B + NOT A B (logic XOR) can be obtained. In the AND (AB ) gate, Boolean NOT B is firstly obtained by using signal B as a pump beam and clock signal as a probe beam in SOA-3. By passing signal A as a probe beam and NOT B as a pump beam through SOA-4, Boolean AB is acquired. By achieving this experiment, we also explored the possibilities for the enhanced complex logic operation and higher chances for multiple logic integration.
Recently, 3D virtual endoscopy has been used as an alternative noninvasive procedure for visualization of a hollow organ. In this paper, we propose a fast volume rendering scheme based on perspective ray casting for virtual endoscopy. As a pre-processing step, the algorithm divides a volume into hierarchical blocks and classifies them into opaque or transparent blocks. Then, the rendering procedure is as follows. In the first step, we perform ray casting only for sub-sampled pixels on the image plane, and determine their pixel values and depth information. In the second step, by reducing the sub-sampling factor by half, we repeat ray casting for newly added pixels, and their pixel values and depth information are determined. Here, the previously obtained depth information is utilized to reduce the processing time. This step is performed recursively until the full-size rendering image is acquired. Experiments conducted on a PC shows that the proposed algorithm can reduce the rendering time by 70-80% for the bronchus and colon endoscopy, compared with the brute-force ray casting scheme. Thereby, interactive rendering becomes more realizable in a PC environment without any specific hardware.
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