Label Bit Research Articles

Investigation of a Silicon Photonic Optical Serial-to-Parallel Converter With Mach–Zehnder Delay Interferometers and Integrated Ge-PDs

A silicon photonic optical serial-to-parallel converter (OSPC) with phase operation, which consists of Mach–Zehnder delay interferometers (MZDIs) with 1- to 8-bit delay lengths, was fabricated for 8-bit processing at 40 Gb/s. The OSPC performs a 1-bit extraction from the packet in each MZDI with a $\pi $ phase bias by interfering a target label bit with a $\pi $ /2-phase-shifted preamble setting at the top of the packet. An improvement in the number of processed bits is verified by introducing an output-side coupler with unequal splitting ratio, which compensates the power unbalance in the MZDI caused by a larger propagation loss in the delay line. We set a splitting ratio of 32:68 as the optimized value, for example, for the 20-bit-delay MZDI, assuming a propagation loss of 2.6 dB/cm. The Si waveguide was 0.50- $\mu \text{m}$ -wide and 0.21- $\mu \text{m}$ -thick, and it was buried in 2- $\mu \text{m}$ -thick lower and upper SiO2 cladding layers. The delay lengths were designed as an integer multiple of the unit length where light propagates in a 1-bit duration, and the unit length was 1.83-mm-long for 40Gb/s data. Thus, the delay length ranged from 1.83 to 14.64 mm for 1- to 8-bit delay MZDIs. Because of the small bending radius of 10- $\mu \text{m}$ , the total device size could be downsized, and it was set to $2~{\rm mm}\times 1.8$ mm. First, we evaluated the transmissivity spectrum of the MZDIs, and free spectral ranges of 40 GHz divided by one to eight were obtained, which were less than 5% deviation from the designed values. The difference of the transmissivity between the upper and the lower output port of the MZDI affects the output signal intensity, and its improvement was investigated by changing the splitting ratio of the output side splitter with various lengths of the multimode interferometers. The control of the transmissivity difference could be confirmed. Next, we investigated a Ge-photodetector (PD) integrated OSPC. We successfully obtained the preliminary results for the OSPC operation in the case of 1-bit delay OSPC with integrated Ge-PDs. The suppression ratios, defined as the ratios of the extracted bit amplitude to the maximum amplitude of the canceled bits, of 11 dB was obtained. The performance could be improved by the optimized splitting ratio of the output-side MMI, the suppression of the input signal chirp, the reduction of insertion loss, and the improvement of the PD sensitivity.

Transmission performance of implicit optical label switching system with coherently detected spectral amplitude code labels

A new optical label switching system with coherently detected implicit spectral amplitude code (SAC) labels is proposed in this paper. The implicit SAC labels are recognized using a frequency-swept local light source oscillator. An explicit SAC-label switching system with 40 Gbit/s intensity modulation (IM) payloads and 156 Mbit/s label and an implicit SAC-label switching system with 2.5 Gbit/s IM payloads and 156 Mbit/s label are both considered. Label and payload bit error rate (BER) performance is assessed and compared by simulations. The results reveal that after 80 km transmission and at the BER of 10−9, the received optical power (ROP) values of label and payload are −8.3 dBm and −23.5 dBm in implicit SAC-label switching system, respectively, while those are −18.2 dBm and −18.6 dBm in explicit SAC-label switching system, respectively. As a result, the payloads of 40 Gbit/s and 2.5 Gbit/s in explicit/implicit SAC-label switching system have little influence on the received payload quality at the BER of 10−9 after 80 km transmission. Finally, a payload of 40 Gbit/s can obtain 12.5 dB optical signal-to-noise ratio (OSNR) after 80 km transmission.

A New Loopback Method of All-Optical Label Processing for Label Bit Scalability

We propose and demonstrate a new method to expand the label bit in an all-optical label processor with a multistage switching fabric. It utilizes a loopback configuration, where a probe pulse is fed back to the same switching fabric with wavelength conversion and the output probe pulse is discriminated by arrayed waveguide gratings. The feasibility of the loopback scheme was demonstrated for the two-bit pattern in the two-bit label using a single semiconductor optical amplifier-based Mach-Zehnder interferometer 1x2 all-optical switch. It is effective to reduce the number of switching elements and will expand the number of label bits.

Experimental Demonstration of a Dynamic 10 G bit/s WDM Header/Label Recognition Structure

In this paper, we experimentally demonstrate a dynamic wavelength-division-multiplexing (WDM) header/label recognition structure that processes on-the-fly WDM patterns. An opto-VLSI processor is used to dynamically generate digital phase holograms that control the wavelength components of the label/header to create digital wavelength profiles. An autocorrelation function of a high-peak is generated when a label bit pattern matches a digital wavelength profile. The main attractive feature of using an opto-VLSI processor is that the lookup table of matching digital wavelength profiles does not need modification when the data bit-rate is upgraded. The dynamic pattern recognition structure is experimentally demonstrated at 10 Gbit/s for 4-, 6-, and 8-bit labels.

All-optical label recognition for time-domain signal using multistage switching scheme based on SOA-MZIs

Proposed is a novel all-optical packet label recognition scheme for a time-domain signal, where all-optical 1×2 switching units are connected in a tree configuration. An optical probe pulse comes out of one of the output ports according to the label bit pattern. Feasibility of the all-optical label recognition was demonstrated for a two-bit label using SOA-MZI all-optical switches.

Performance monitoring in transparent optical networks using self-monitoring optical-labels

A novel optical layer performance monitoring method in transparent optical-label switching networks is presented. It is based on the signal quality correlation between the data payload and the label, which allows monitoring of the data payload signal quality by monitoring the label bit error rates. Experimental results indicate effective estimations of payload data bit error rates over approximately a 15 dB dynamic range of signal-to-noise ratio.

Optimal differential energy watermarking of DCT encoded images and video

This paper proposes the differential energy watermarking (DEW) algorithm for JPEG/MPEG streams. The DEW algorithm embeds label bits by selectively discarding high frequency discrete cosine transform (DCT) coefficients in certain image regions. The performance of the proposed watermarking algorithm is evaluated by the robustness of the watermark, the size of the watermark, and the visual degradation the watermark introduces. These performance factors are controlled by three parameters, namely the maximal coarseness of the quantizer used in pre-encoding, the number of DCT blocks used to embed a single watermark bit, and the lowest DCT coefficient that we permit to be discarded. We follow a rigorous approach to optimizing the performance and choosing the correct parameter settings by developing a statistical model for the watermarking algorithm. Using this model, we can derive the probability that a label bit cannot be embedded. The resulting model can be used, for instance, for maximizing the robustness against re-encoding and for selecting adequate error correcting codes for the label bit string.