T. Ohno

Measurement of intermodulation distortion in a unitraveling-carrier refracting-facet photodiode and a p-i-n refracting-facet photodiode

In this letter, we present an experimental characterization of third-order intermodulation distortion (IM3) at 5.8 GHz in a unitraveling-carrier refracting-facet photodiode (UTC-RFPD) and a p-i-n refracting-facet photodiode (pin-RFPD). The IM3 in the pin-RFPD is considerably reduced compared to the waveguide-type p-i-n photodiode. The third-order intercept point (IP3) of the UTC-RFPD does not decrease as the photocurrent increases, indicating that space-charge-induced nonlinearity is well suppressed in this photodiode. The two-tone IP3 of the UTC-RFPD estimated from the measurement reaches a very high level of 40.5 dBm.

Application of DBR mode-locked lasers in millimeter-wave fiber-radio system

An actively mode-locked laser (MLLD) integrated with a distributed Bragg reflector (DBR) was used as a light source for optical subcarrier transmission. The millimeter (mm)-wave power penalty due to fiber dispersion is suppressed within 4 dB by operating this laser in a symmetric four-mode configuration. The experimental results agree well with the calculation of dispersion-induced penalty for a four-component-lightwave source. Optical subcarrier transmission free from dispersion-induced penalty within experimental error is achieved by further suppression of the end-modes of the DBR-MLLD using a fiber Bragg grating (FBG).

A 240-GHz active mode-locked laser diode for ultra-broadband fiber-radio transmission systems

A 240-GHz optical millimeter-wave signal with very narrow linewidth (<10 Hz) is generated using an active mode-locked laser diode integrated with a high-mesa electroabsorption modulator. Fiber-radio transmission of 3-Gbit/s data at 240 GHz is also demonstrated.

Phase shift keying using optical delay modulation for millimeter-wave fiber-optic radio links

We propose a novel phase shift keying technique that uses optical delay modulation for fiber optic radio links. Using only a 2/spl times/1 switch and a delay line, this technique enables modulation of a millimeter-wave carrier at bit rates of several gigabits per second or higher, where high-speed devices are not needed. Binary phase shift keying (BPSK) was experimentally demonstrated, 2-Gb/s data signal on a 40-GHz carrier was transmitted over a 5-km optical fiber without any error. The coherent crosstalk noise, due to insufficient extinction ratio of optical switches, was evaluated. The BPSK modulation technique can he extended to multiphase shift-keying modulation.

Frequency stabilization of millimeter-wave subcarrier using laser heterodyne source and optical delay line

A frequency stabilization technique for laser heterodyne sources that is applicable to fiber-radio systems is experimentally demonstrated, It employs an optical delay line as a frequency reference instead of a millimeter-wave oscillator. A subcarrier signal with a 12.3-MHz deviation was generated in a 10-GHz band by using commercial-grade DFB-LDs.

Compact ROSA for 100-Gb/s (4 × 25 Gb/s) Ethernet with a PLC-based AWG demultiplexer

We report a compact receiver optical sub-assembly (ROSA) for 100GbE CFP4 transceivers. All the four channels of fabricated module exhibits wide wavelength passband and high receiver sensitivity enough for 10-km-reach transmission.

Dual mode operation of semiconductor mode-locked lasers for anti-phase pulse generation

Anti-phase pulse generation at 40 and 60 GHz have been demonstrated using dual-mode semiconductor mode-locked lasers. Suppression of pulse distortion due to fiber dispersion is confirmed for generated anti-phase pulses.

Third-order intermodulation distortion characteristics of a non-biased electroabsorption modulator on fiber-radio system

The third-order intermodulation distortion characteristics of an electroabsorption modulator that operates at zero bias voltage were investigated. Spurious free dynamic range was sufficiently high to realize an uplink access point on fiber-radio without a DC electric power supply.

Bi-directional optical microwave transmission using a base station without DC electric power supply

Bi-directional optical microwave transmission was performed using a base station composed of a bias free electric absorption modulator and a uni-traveling carrier photodiode. Error free operation was performed for down- and up-stream data links.

A CAN-type MIC-PD ROSA operating at 40-Gbit/s

We fabricated a 40-Gbit/s CAN-type ROSA using a maximized-induced-current photodiode (MIC-PD). 40-Gbit/s error-free operation was achieved for the first time with a CAN-type ROSA, owing to the high-speed capability of the MIC-PD and impedance matching of glass feedthrough.