All-optical ultra-wideband pulse generation based on semiconductor optical amplifiers

Abstract

Several all-optical methods for ultra-wideband (UWB) pulse generation based on various nonlinearities of single semiconductor optical amplifiers (SOAs), namely cross phase modulation (XPM), cross gain modulation (XGM), and a hybrid of self phase modulation (SPM) and XGM, have been demonstrated. In the first method, UWB doublet pulses are realized with XPM. The input optical Gaussian pulse will be converted to two polarity-reversed monocycle pulses by a blue shifted and a red shifted optical bandpass filters respectively. These two monocycle pulses are then combined with proper time delay to generate two polarity-reversed doublet pulses. Second, two polarityreversed monocycle pulses are obtained based on XGM of the SOA and group delay of the single mode fiber (SMF). In the scheme, two polarity-reversed Gaussian pulses are generated due to XGM, and then the mixed signal is converted to a monocycle shape due to the group delay of the SMF. Finally, we present UWB doublet generation based on SPM. The monocycle pulse is generated from a dark return-to-zero (RZ) signal and converted to a doublet pulse by injecting an additional probe signal with the SMF transmission. For the first time and to the best of our knowledge, we report that the generated doublet pulses are transmitted over 5 km SMF by proper dispersion compensation without distortion. The configuration of our alloptical methods is compact and simple. The feasibility to implement the pulse shape modulation and pulse polarity modulation is discussed.

Semiconductor Optical Amplifiers

“…Its value may be positive or negative. UWB doublet pulses can be obtained by combining positive and negative monocycles with a proper delay Dong (2009). The shortages of the proposed method are the necessity for complicated electronic circuit for generation short electric Gaussian pulses, the use of an electro-optic phase modulator (EOM), the need for a comparatively long singlemode fiber (SMF), and a comparatively low operation rate and high bias currents of bulk SOAs.…”

All Optical Generation and Processing of IR UWB Signals

“…When the Gaussian pulses (8) and the probe signal are simultaneously fed into SOA, the probe signal will undergo both XGM and XPM, and the phase Φ c is varying approximately proportionally to P s (t) Dong (2009) …”

“…The SOA is followed by Gaussian optical blue shifted optical bandpass filter (OBF) and red shifted OBF forming the two polarity-reversed monocycle pulses with an opposite detuning to the probe carrier λ c . Then, UWB doublet pulses can be obtained by combining the positive and negative monocycles with a proper delay Dong (2009). EDFA is necessary to amplify the output optical signal power due to large loss of OBFs, and OBF at the output with 1nm bandwidth is used in order to suppress the amplified spontaneous emission (ASE) noise Dong (2009).…”

“…Then, UWB doublet pulses can be obtained by combining the positive and negative monocycles with a proper delay Dong (2009). EDFA is necessary to amplify the output optical signal power due to large loss of OBFs, and OBF at the output with 1nm bandwidth is used in order to suppress the amplified spontaneous emission (ASE) noise Dong (2009). The necessity of OBFs and EDFA makes the UWB pulse generation system based on XPM a costly one Dong (2009).…”

“…EDFA is necessary to amplify the output optical signal power due to large loss of OBFs, and OBF at the output with 1nm bandwidth is used in order to suppress the amplified spontaneous emission (ASE) noise Dong (2009). The necessity of OBFs and EDFA makes the UWB pulse generation system based on XPM a costly one Dong (2009). Two polarity-reversed pulses can be obtained with a pump-probe scheme based on XGM in SOA where the time delay between the pump and probe waves is appropriately chosen.…”