An Approach to a Method of Construction of (F, K, 1) Optical Orthogonal Codes from Block Design

F, K, 1) Optical orthogonal codes (OOC) are the best address codes applied to optical code division multiple access (OCDMA) communication systems, but the construction of the codes is very complex. In this paper, a method of construction of the OOC from block design is discussed and a method of computer aid design is presented, by which we can construct desired (F, K, 1) OOC easily.

A passive optical network based on optical code division multiplexing and time division multiple access technology

A passive optical network （PON） scheme based on optical code division multiplexing （OCDM） for the downstream traffics is proposed and analyzed in detail. In the PON, the downstream traffics are broadcasted by OCDM technology to guarantee the security, while the upstream traffics pass through the same optical fiber by the common time division multiple access （TDMA） technology to decrease the cost. This schemes are denoted as OCDM/TDMA-PON, which can be applied to an optical access network （OAN） with full services on demand, such as Internet protocol, video on demand, tele-presence and high quality audio. The proposed OCDM/TDMA-PON scheme combines advantages of PON, TDMA, and OCDM technology. Simulation results indicate that the designed scheme improves the OAN performance, and enhances flexibility and scalability of the system.

Maximum two-dimensional (u×v,4,1,3)-OOCs

Let Ф（u ×v, k, Aa, Ac） be the largest possible number of codewords among all two- dimensional （u ×v, k, λa, λc） optical orthogonal codes. A 2-D （u× v, k, λa, λ）-OOC with Ф（u× v, k, λa, λc） codewords is said to be maximum. In this paper, the number of codewords of a maximum 2-D （u × v, 4, 1, 3）-OOC has been determined.

Construction of deterministic sensing matrix and its application to DOA estimation

Compressive sensing（CS） has emerged as a novel sampling framework which enables sparse signal acquisition and reconstruction with fewer measurements below the Nyquist rate.An important issue for CS is the construction of measurement matrix or sensing matrix.A new deterministic sensing matrix,named as OOC-B,is proposed by exploiting optical orthogonal codes（OOCs）,Bernoulli matrix and Singer structure,which has the entries of 0,＋1 and-1 before normalization.We have proven that the designed deterministic matrix is asymptotically optimal.In addition,the proposed deterministic sensing matrix is applied to direction of arrival（DOA） estimation of narrowband signals by CS arrays（CSA）processing and CS recovery.Theoretical analysis and simulation results show that the proposed sensing matrix has good performance for DOA estimation.It is very effective for simplifying hardware structure and decreasing computational complexity in DOA estimation by CSA processing.Besides,lower root mean square error（RMSE） and bias are obtained in DOA estimation by CS recovery.

A New Performance Analysis Method of Optical Code Division Multiple Access Systems with An Optical Hard-Limiter

A new performance analysis method of Optical Code Division Multiple Access ( OCDMA ) systems with an optical hard limiter is studied. The bit error probability of the OCDMA system is derived, and the numerical results of the system with and without an ideal optical hard limiter are analyzed respectively. The results show that although the derived expression is different from the one derived by J A Salehi , the numerical results are the same as those analyzed by J A Salehi, and the numerical result can be easily achieved in this expression.

Performance Analysis of 32-User Spectral Phase Encoding Time Domain System for Fiber-Optic CDMA Networks

Multiple access techniques are required to meet the demand for high-speed and large-capacity commtmications in optical networks, which allow multiple users to share the fiber bandwidth. O-CDMA （optical code-division multiple-access） is receiving increased attention due to its potential apphcations for LAN optical networks. O-CDMA is attractive for next generation broadband access networks due to its features of allowing fully asynchronous transmission with low latency access, soft capacity on demand, protocol transparency, simplified network management as well as increased flexibility of QoS （Quality of Service） control and enhanced confidentiahty in the network. Hence, the authors experimentally investigate an ultra short pulse O-CDMA scheme based on spectral phase encoding and decoding of coherent mode-locked laser pulses, they proposed a technique using spectral phase encoding time domain system for 32 users. This technique is proved to be much effective to handle 32 users at 4 Gb/s bit rate and 60 km SMF （single mode fiber） transmission used for SPE O-CDMA system. Results indicate significant improvement in term low BER （beat error rate） and very high quality factor in the form of QoS. The authors have used PSO （pseudo orthogonal） codes and random phase code. The simulations are carried out using OptSim （RSOFT）.

Optical PPM-CDMA Communication System with Optical Hard Limiter

An optical PPM CDMA communication system with an optical hard limiter in front of the correlator of a receiver is proposed in order to reduce multi user interference. The performance of the system is evaluated when the effects of both multi user interference and photo detector shot noise are considered. An upper bound on the bit error rate is derived. The comparison of the performance of the above receiver with that of the optical PPM CDMA system without an optical hard limiter is made. Simulation results show that the performance of the system with an optical hard limiter is superior to that of the conventional one.

Constructions of optimal variable-weight OOCs via quadratic residues

Variable-weight optical orthogonal code （OOC） was introduced by G. C. Yang [IEEE Trans. Commun., 1996, 44： 47-55] for multimedia optical CDMA systems with multiple quality of service （QoS） requirements. In this paper, seven new infinite classes of optimal （v, {3,4,6}, 1, Q）-OOCs are constructed.

The Existence of (v,4,1) Disjoint Difference Families with a Prime Power

A （v, k, λ） difference family （（v, k, λ）-DF in short） over an abelian group G of order v, is a collection F=（Bi｜i ∈ I} of k-subsets of G, called base blocks, such that any nonzero element of G can be represented in precisely A ways as a difference of two elements lying in some base blocks in F. A （v, k, λ）-DDF is a difference family with disjoint blocks. In this paper, by using Weil＇s theorem on character sum estimates, it is proved that there exists a （p^n, 4, 1）-DDF, where p = 1 （rood 12） is a prime number and n ≥1.