A multi-wavelength integrated device (5) including plural semiconductor lasers (6) and plural modulators (7) modulating output beams of the plural semiconductor lasers (6) respectively is mounted on the stem (1). Plural leads (10) penetrates through the stem (1) and are connected to the plural semiconductor lasers (6) and the plural modulators (7) respectively. Each lead (10) is a coaxial line in which plural layers are concentrically overlapped with one another. The coaxial line includes a high frequency signal line (12) transmitting a high frequency signal to the modulator (7), a GND line (14), and a feed line (16) feeding a DC current to the semiconductor laser (6). The high frequency signal line (12) is arranged at a center of the coaxial line. The GND line (14) and the feed line (16) are arranged outside the high frequency signal line (12).

A multi-wavelength integrated device (5) including plural semiconductor lasers (6) and plural modulators (7) modulating output beams of the plural semiconductor lasers (6) respectively is mounted on the stem (1). Plural leads (10) penetrates through the stem (1) and are connected to the plural semiconductor lasers (6) and the plural modulators (7) respectively. Each lead (10) is a coaxial line in which plural layers are concentrically overlapped with one another. The coaxial line includes a high frequency signal line (12) transmitting a high frequency signal to the modulator (7), a GNU line (14), and a feed line (16) feeding a DC current to the semiconductor laser (6). The high frequency signal line (12) is arranged at a center of the coaxial line. The GND line (14) and the feed line (16) are arranged outside the high frequency signal line (12).