## 1 Introduction  
Optical fibre networks are a vital means of modern communication. Today's applications demand high data rate throughputs and this demand continues to increase. With incoherent data communication approaches, high data rates demand the use of short optical pulses as data carriers. An effective management of these short optical pulses, mainly their temporal broadening due to dispersion effects in optical fibre, is becoming increasingly challenging. It has been observed that the signals are 16 times more sensitive to chromatic dispersion at 40 Gb/s when compared to that at 10 Gb/s [1]. Therefore, to meet user demands for a much higher transmission bandwidth, the network operators face the challenge of how to adapt the existing networks to support the higher data rates that are demanded. However, without having simple ways to achieve tunable chromatic dispersion (CD) management, the current solution depends on accurate fibre length adjustments between different transmission fibre types and dispersion compensating fibre (DCF). The main disadvantage is the bulky nature of this approach. Another cost-effective and commonly used method of compensation is the use of fibre Bragg gratings (FBGs) [2]. Some other approaches include using new modulation schemes, chirp pre-compensation, electronic dispersion compensation, and the use of digital filters etc. [2; 3; 4]. Optical code division multiple access (OCDMA) is an advanced multiplexing scheme that is attractive for its high scalability and random access [5]. One of efficient and often used coding schemes by incoherent OCDMA systems is a two-dimensional wavelength-hopping time-spreading (2D-WH/TS) coding [6; 7]. In this encoding approach, OCDMA sequences are spread simultaneously in both wavelength and time domains in order to improve the system scalability and its performance [5; 6; 8]. A 2D-WH/TS prime code is a class of two dimensional (2D: wavelength-time), incoherent asynchronous codes that support wavelength hopping within time-spreading over the Galois field of prime numbers with zero auto-correlation side-lobes and periodic cross-correlation functions of at most one [5]. Because 2D-WH/TS systems use multi-wavelength short picosecond code carriers, the data transmission is susceptible to the presence of chromatic dispersion in optical fibre [9]. Therefore, it is imperative to understand the influence of dispersion and to also have relatively simple means for dispersion mitigation. If untreated, the recovered OCDMA auto-correlation function (i.e., the received data pulse envelope) that is recovered by a CDMA receiver's decoder will be distorted and broadened due to code carriers' time-skewing [10], which is caused by chromatic dispersion in optical fibres. The multi-wavelength optical pulses that are used as OCDMA code carriers travel with different speeds since the fibre refractive index is wavelength dependent. Here also DCF modules are commonly used for CD compensation. However, the use of picosecond code carriers demands a high (sub-picosecond) dispersion compensation accuracy [11]. This is not a very practical approach if a short length of SMF-28 has to be added, requiring compensation by matching the length of the DCF fibres. There is therefore a widely recognized need for tunable dispersion compensation techniques. Different types of tunable dispersion compensators, such as integrated tunable chirped fibre Bragg gratings (CFBG), adaptive tunable dispersion control, dispersion equalization by adjusting the equalizer to maximize the clock component, virtually imaged phase arrays (VIPA), micro electro mechanical systems (MEMS), and other methods were demonstrated [12; 13; 14; 15; 16; 17]. The use of Semiconductor Optical Amplifiers (SOAs) has also been investigated for tunable dispersion control for use in incoherent OCDMA systems. In [18; 19], an SOA that was located at the receiver site was investigated for its effectiveness in reshaping the OCDMA auto-correlation functions distorted by the dispersion.