In this work, the performance of a tap selection based Minimum Mean Square Error (MMSE) equalization technique for high data rate Ultra Wideband (UWB) systems is evaluated for the first time using greedy method. This technique is shown to significantly outperform the conventional uniformly spaced equalizer with the same number of taps. In addition, the performance of strongest paths based tap selection method is compared with the greedy method. Larger performance gap is observed in the presence of Multiple Access Interference (MAI) and with increased SNR.
An efficient short wavelength band erbium-doped fiber amplifier (S-band EDFA) is proposed and demonstrated using double-pass configuration. This amplifier provides a gain as high as 30dB, but using only 15m depressed cladding erbium-doped fiber (EDF) and 130mW of 980nm pump power. Compared to the single-pass configuration, this amplifier shows a gain enhancement of about 14dB for pump powers above 120mW. However, noise figures penalties of about 0.5 ∼ 0.9dB are obtained for these pump powers. The proposed double-pass amplifier will play an important role in the development of a practical S-band EDFA from perspective of economical usage of EDF and pump power.
A gain-clamped short wavelength band erbium-doped fiber amplifier (S-band EDFA) is demonstrated utilizing a fiber Bragg grating (FBG). The amplification in S-band is achieved using an erbium-doped fiber (EDF) with depressed cladding design, which suppressed amplified spontaneous emission (ASE) at longer wavelength. The gain clamping is achieved by routing back the forward ASE into the feedback loop as to create a ring laser. The clamped gain is controlled using a variable optical attenuator (VOA) as to generate a gain of 14.6 to 25.2dB for input signal at 1504nm. At VOA = 0dB, the gain is clamped at 14.6dB with a gain variation of less than ±0.5dB for input signal at 1504nm with power dynamic range of -40 to -5dBm. The noise figure penalty is less than 0.8dB in this amplifier since the laser is arranged to be co-propagated with the signal.
The crosstalk effects in a subcarrier multiplexed-wavelength division multiplexed (SCM-WDM) system due to cross phase modulation (XPM) have been investigated. The variation of XPM induced distortion is investigated for parameters such as transmission distance, frequency and channel spacing. Results show that the XPM induced dispersion in an SCM-WDM system is directly proportional to the transmission distance and frequency and inversely proportional to the channel spacing.
The noise characterization of a capacitive servo-accelerometer using a linear model is presented in this paper. The input reference noise of electronic circuit is expressed as a capacitive variation and it is introduced to a linear model for frequency response, separately with the thermal mechanical noise. The simulated noise was generally found to conform to the measured noise in the experiment, suggesting that the model can be effectively used for noise evaluation of accelerometers fabricated in a similar fashion.
A novel test methodology is established to evaluate the strain relief boot on optoelectronic components and optical fiber components by measuring the fiber bend radius in side pull test. The technique is developed for qualifying the boot design rather than for lot testing. The criterion and process are provided.
This letter newly proposes a new multi-user detection scheme for multiple users using co-channel heterogeneous radio signals in ubiquitous antenna system. The ubiquitous antenna system is composed of multiple radio base stations (RBSs), the central control station (CCS) which performs the multi-user detection, and radio-on-fiber (RoF) link which connects the RBSs to the CCS. Computer simulation results show that the multi-user detector exploiting the minimum mean square error (MMSE)-based combiner and the serial interference canceller (SIC) in combination can achieve the coexistence of coded orthogonal frequency division multiplexing (COFDM) and direct sequence spread spectrum (DSSS) signals.