Spectral phase-encoded time-spreading (SPECTS) optical code-division multiple access for terabit optical access networks

An eight-user time-slotted SPECTS O-CDMA testbed: demonstration and simulations

“…The typical power contrast ratio between correctly and incorrectly decoded pulses is better than 20 dB. For additional details of the thresholder operation, see [10] and [13]. During initial measurements of the testbed at 10 Gb/s, ∼ 4% spurious reflections were discovered coming from the first surface of the LC-SLPM at ±49 ps from the incident pulse.…”

“…In either case, the codes are chosen to have the most favorable cross-correlation and autocorrelation characteristics in order to minimize channel crosstalk, also known as multiaccess interference (MAI) or multiuser interference (MUI). This paper investigates 1-D codes applied in the spectral domain called spectral phase-encoded time-spreading (SPECTS) O-CDMA [10]. In SPECTS O-CDMA, encoding is accomplished by phase shifting individual slices (i.e., chips) of a pulse's optical spectrum [11], [12].…”

“…Slotted operation increases the spectral efficiency for a given data rate and allows code reuse (i.e., the same code can be used in different time slots), thus increasing the possible number of simultaneous users for a given code size. Previous works [10], [13] relied on a highly nonlinear fiber (HNLF)-based thresholder [14] to suppress MUI. For the time-slotted testbed, gated detection becomes necessary, and this paper discusses two types: an ultrafast nonlinear interferometer (UNI) and a nonlinear optical loop mirror (NOLM) time gate.…”

Arrayed-waveguide grating with wavefront compensation lenses for spatial filter integration

“…Various kinds of photonic signal processing, such as dispersion compensation, short pulse generation, pulse shaping, and optical packet generation can be realized by time-to-space conversion and spatial filtering [1,2,3,4]. An arrayed-waveguide grating (AWG) [5] is especially suitable for this technique because of its high resolution, simultaneous demultiplexing of all channels, and ease of integration.…”

Bit-error-rate analysis of a 16-user gigabit ethernet optical-CDMA (O-CDMA) technology demonstrator using wavelength/time codes

“…O-CDMA schemes are categorized as implementing the code through the optical field and relying on coherent detection, or through time slots and wavelengths with reliance on incoherent detection. Coherent schemes are susceptible to coherent beat noise that occurs when the correctly decoded signal temporally overlaps with the multiple access interference (MAI) from other users [1]. Thus, recent implementations of coherent O-CDMA resort to timing coordination between users, ranging from complete bit-level synchronization [2] to time slot assignment within the bit [3].…”