Gyu-Woong Lee

1-fiber WDM self-healing ring with bidirectional optical add/drop multiplexers

We propose a 1-fiber bidirectional WDM self-healing ring that has bidirectional optical add/drop multiplexers. A simple fault detection method is proposed, and no signal degradation due to in-band crosstalk is demonstrated in the failure state. The power penalty of the ring transmission was less than 1 dB at a BER 10/sup -12/ in the normal and failure state.

On the use of 2.5-Gb/s Mach-Zehnder modulators to generate 10-Gb/s optical duobinary signals

We demonstrate the generation of 10-Gb/s optical duobinary signals from 2.5-Gb/s Mach-Zehnder (MZ) modulators without using duobinary encoders. The absence of the duobinary encoder not only permits the monolithic integration of electrical components but also reduces the required bandwidth of MZ modulators as low as 3 GHz. However, it might induce pattern-length dependency to the signals. Our demonstration, performed with four 2.5-Gb/s MZ modulators obtained from two different vendors, shows that the receiver sensitivity of better than -33.8 dBm is achieved at a pseudorandom bit sequence length of 2/sup 31/-1 when dispersion of 1200 /spl sim/ 1700 ps/nm is applied to the signals. This is 1.6 dB poorer than using an 8.5-GHz bandwidth MZ modulator along with a 3.0-GHz Bessel filter. Therefore, this scheme can be used to implement cost-effective 10-Gb/s optical duobinary transmitters without significant performance degradation.

RoF Technologies for In-Building Wireless Systems

This paper reports on a fiber-optic system for in-building wireless communication/broadcast systems developed in Samsung Electronics. Our system delivers the third generation mobile system, satellite-digital multimedia broadcast, and wireless local access network services over a single strand of single-mode fiber or multi-mode fiber. We present the design issue and experimental results of the radio-over-fiber link.

Cost-effective optical chirped duobinary transmitter using an electroabsorption modulated laser

We propose and demonstrate a cost-effective way to implement a 10-Gb/s chirped duobinary (CDB) transmitter using an electroabsorption modulated laser (EML) followed by a LiNbO/sub 3/ Mach-Zehnder modulator both driven with binary signals. Successful transmission is achieved over 285 km of dispersion-uncompensated standard single-mode fiber without significantly increasing the complexity and cost of the transmitter, compared to conventional duobinary transmitters. The demonstrated CDB signals exhibit a superior performance to conventional duobinary signals, in terms of back-to-back receiver sensitivity and transmission distance. We achieve consistent transmission performance with three EMLs obtained from two different vendors, each having different chirp and transmission characteristics. Therefore, we believe the use of EMLs greatly reduces the implementation issues of 10-Gb/s CDB transmission systems.

Cost-effective 10-Gb/s optical duobinary transmission systems using a nonbuffered X-cut LiNbO/sub 3/ Mach-Zehnder modulator

We demonstrate a cost-effective method to implement a 10-Gb/s optical duobinary transmitter using a simple nonbuffered x-cut LiNbO/sub 3/ Mach-Zehnder (MZ) modulator. The bandwidth of the modulator used in our experimental demonstration is 4 GHz. The duobinary signal generated from the nonbuffered MZ modulator exhibits a similar performance to the one using a 9-GHz bandwidth buffered MZ modulator, in terms of dispersion and self-phase modulation tolerance. Thus, the use of cost-effective nonbuffered x-cut MZ modulators will substantially relax the cost issues of duobinary transmitters, by offsetting the cost of the precoder and the encoder which are not needed in conventional on-off keying transmitters.

Switch Controlled Source Amplifier for Low Power Mobile TFT-LCD Driver IC

Switch controlled source amplifier (SCSA) is proposed for low power mobile TFT-LCD driver ICs (T-LDIs). In SCSA scheme, the operation of the source drivers in a T-LDI is determined by the source line load of TFT-LCD. That is, output stage current of source buffers is reduced when the source line load is separated for current saving operation such as charge sharing between VCOM and source lines. With SCSA scheme, all the static current of source buffers can be reduced as far as phase margin of the output buffers is permitted. A test chip was fabricated in a 5-V/0.8-mum triple-metal CMOS process with QVGA resolution, and the experimental results show that the power consumption of 11%~16% was saved with die size overhead less than 1%.

Cost-effective optical duobinary transmitters

This paper presents several ways to implement cost-effective optical duobinary transmitters using low-cost optical modulators. We show that, compared to the conventional scheme, the proposed schemes can be used to implement cost-effective duobinary transmission systems without a significant sacrifice of system performance.