Optical modulator and optical transmission device using same

Abstract

In an optical modulator in which a circuit element is provided on a relay substrate, the influence of leaked microwaves generated from the relay substrate is reduced and good modulation characteristics are achieved. An optical modulator (100) is provided with: an optical modulation element (102) provided with a plurality of signal electrodes (112a-112d), the optical modulation element (102) being configured so as to generate two beams of modulated light each modulated by two sets of electrical signals, each set of electrical signals including two electrical signals; a plurality of signal input terminals (124a-124d) for inputting an electric signal; a relay substrate (618) on which a plurality of signal conductor patterns (630a-630d) and a plurality of ground conductor patterns (640a-640d) are formed, the relay substrate (618) transmitting two sets of electrical signals through two pairs of adjacent signal conductor patterns; and a housing (104), in the optical modulator (100), at least two signal conductor patterns provided with at least one component mounting portion including the circuit components (350a-350d) are configured such that first signal transmission directions, which are signal transmission directions at the component mounting portion, are different from each other.

Description

technical field [0001] The present invention relates to an optical modulator including a relay substrate for relaying transmission of an electrical signal between a signal input terminal and a signal electrode of an optical modulation element, and an optical transmission device using the optical modulator. . Background technique [0002] In a high-speed / large-capacity optical fiber communication system, an optical modulator incorporating a waveguide-type optical modulation element is frequently used. Among them, LiNbO with photoelectric effect 3 (Hereinbelow, also referred to as LN) The light modulation element used for the substrate can realize light modulation characteristics with little loss of light and broadband, and thus is widely used in high-speed / large-capacity optical fiber communication systems. [0003] In this optical modulation element using an LN substrate, a Mach-Zehnder type optical waveguide and a signal electrode for applying a high-frequency electrical ...

AI Technical Summary

Problems solved by technology

[0017] However, the above-mentioned component mounting portion 2250 may cause the high-frequency (microwave) propagating through the signal conductor pattern 2230 due to, for example, a difference in the physical shape of the circuit element and the signal conductor pattern 2230, or a deviation in the mounting position of the circuit element. disordered electrical signaling

As a result, a part of the above-mentioned microwave electric signal leaks from the component mounting part 2250, and becomes a leaked microwave 2290 ( Figure 14 ), for the adjacent signal conductor pattern 2230 and the signal electrode 2212 on the light modulation element 2202, it may act as noise

[0018] In addition, as described above, in the above-mentioned structure in which the component mounting portions 2250 are arranged at approximately the same interval and facing the same direction, the leaked microwaves leaking from each component mounting portion 2250 may have a direction substantially facing each other. Directional transmission in the same direction

Moreover, in the case of an optical modulator that generates two beams of modulated light modulated by a pair of high-frequency electrical signals, such as a DP-QPSK optical modulator, not only does the above-mentioned high-frequency signal change between the paired high-frequency electrical signals The phases are substantially the same, and different pairs also have substantially the same high-frequency components, so leaked microwaves with substantially the same phase and frequency components may be radiated from the component mounting portion 2250

[0019] As a result, the leaked microwaves strongly interfere with each other, and a new problem that has not been thought of in the conventional 100 Gb / s transmission will occur as follows: For the signal electrode 2212 of the surrounding signal conductor pattern 2230 and the optical modulation element 2202 connected thereto Electrical noise comes into play

In addition, when a part of the signal conductor pattern 2230 is recoupled from the leaked microwave generated from the component mounting part 2250 constituting the electric filter to its own signal conductor pattern 2230 and the signal electrode 2212 of the optical modulation element 2202 connected thereto, not only Acts as electrical noise, and also causes additional problems such as deterioration or change of the filter characteristics of the above-mentioned electrical filter

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