# US 12,015,247 B2 · Optical transmission apparatus

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- Number: US 12,015,247 B2
- Document ID: US12015247B2
- Status: Granted
- Kind: B2
- Application number: 17/283,543
- Filed: 2019-12-05
- Published: 2021-12-16
- Granted: 2024-06-18
- Earliest claimed: 2018-12-25
- Assignees: Mitsubishi Electric Corporation
- Applicants: Mitsubishi Electric Corporation
- Inventors: Shusaku Hayashi; Satoshi Nishikawa; Koichi Akiyama
- Web page: https://patentgrep.com/patent/US12015247B2

## CPC

- G02F 1/01708: {in an optical wavequide structure}
- H01S 5/343: in AIIIBV compounds, e.g. AlGaAs-laser {, InP-based laser}
- G02F 1/025: in an optical waveguide structure (G02F1/017, {G02F1/2257} take precedence)
- G02F 1/212: {Mach-Zehnder type}
- H01S 5/50: Amplifier structures not provided for in groups H01S5/02 - H01S5/30
- H04B 10/505: {using external modulation}
- H04B 10/556: Digital modulation, e.g. differential phase shift keying [DPSK] or frequency shift keying [FSK]
- G02F 2203/70: Semiconductor optical amplifier [SOA] used in a device covered by G02F
- H01S 5/0265: {Intensity modulators (intra-cavity modulators H01S5/0625)}
- H01S 5/1007: {Branched waveguides}
- H01S 5/2224: {semi-insulating semiconductors}
- H01S 5/2275: {mesa created by etching}
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H04B: TRANSMISSION

## Abstract

An optical transmission apparatus includes a first multilevel optical phase modulator and a first semiconductor optical amplifier. The first semiconductor optical amplifier includes a first active region having a first multiple quantum well structure. Assuming that a first number of layers of a plurality of first well layers is defined as n1 and a first length of the first active region is defined as L1 (μm): (a) n1=5 and 400≤L1≤563; (b) n1=6 and 336≤L1≤470; (c) n1=7 and 280≤L1≤432; (d) n1=8 and 252≤L1≤397; (e) n1=9 and 224≤L1≤351; or (f) n1=10 and 200≤L1≤297.

## Claims

### Claim 1

An optical transmission apparatus comprising:
a first multilevel optical phase modulator; and
a first semiconductor optical amplifier to amplify first multilevel optical signal lights output from the first multilevel optical phase modulator, wherein
the first semiconductor optical amplifier includes a first active region, and the first active region has a first multiple quantum well structure,
wherein a first number of all well layers of the first multiple quantum well structure is defined as n1 and a first length of the first active region is defined as L1 (μm),
n1=5 and 400≤L1≤563,
n1=6 and 336≤L1≤470,
n1=7 and 280≤L1≤432,
n1=8 and 252≤L1≤397,
n1=9 and 224≤L1≤351, or
n1=10 and 200≤L1≤297.

### Claim 2 (depends on 1)

The optical transmission apparatus according to claim 1, wherein
n1=5 and 500≤L1≤563,
n1=6 and 420≤L1≤470,
n1=7 and 350≤L1≤432,
n1=8 and 315≤L1≤397,
n1=9 and 280≤L1≤351, or
n1=10 and 250≤L1≤297.

### Claim 3 (depends on 1)

The optical transmission apparatus according to claim 1, wherein
n1=5 and 400≤L1≤500,
n1=6 and 336≤L1≤400,
n1=7 and 300≤L1≤400, or
n1=8 and 300≤L1≤397.

### Claim 4 (depends on 1)

The optical transmission apparatus according to claim 1, wherein the first semiconductor optical amplifier is controlled to operate in a gain saturation region of the first semiconductor optical amplifier.

### Claim 5 (depends on 1)

The optical transmission apparatus according to claim 1, further comprising a semiconductor laser to output light to the first multilevel optical phase modulator, wherein
the first multilevel optical phase modulator, the first semiconductor optical amplifier, and the semiconductor laser are formed on a single semiconductor substrate.

### Claim 6 (depends on 1)

The optical transmission apparatus according to claim 1, further comprising:
an optical demultiplexer including an optical input portion, a first optical output portion, and a second optical output portion;
a second multilevel optical phase modulator; and
a second semiconductor optical amplifier to amplify second multilevel optical signal lights output from the second multilevel optical phase modulator, wherein
the first multilevel optical phase modulator is optically connected to the first optical output portion,
the second multilevel optical phase modulator is optically connected to the second optical output portion,
the second semiconductor optical amplifier includes a second active region, and the second active region has a second multiple quantum well structure, and
wherein a second number of all well layers of the second multiple quantum well structure is defined as n2 and a second length of the second active region is defined as L2 (μm),
n2=5 and 400≤L2≤563,
n2=6 and 336≤L2≤470,
n2=7 and 280≤L2≤432,
n2=8 and 252≤L2≤397,
n2=9 and 224≤L2≤351, or
n2=10 and 200≤L2≤297.

### Claim 7 (depends on 6)

The optical transmission apparatus according to claim 6, wherein
n2=5 and 500≤L2≤563,
n2=6 and 420≤L2≤470,
n2=7 and 350≤L2≤432,
n2=8 and 315≤L2≤397,
n2=9 and 280≤L2≤351, or
n2=10 and 250≤L2≤297.

### Claim 8 (depends on 6)

The optical transmission apparatus according to claim 6, wherein
n2=5 and 400≤L2≤500,
n2=6 and 336≤L2≤400,
n2=7 and 300≤L2≤400, or
n2=8 and 300≤L2≤397.

### Claim 9 (depends on 6)

The optical transmission apparatus according to claim 6, wherein
the second number of layers n2 is equal to the first number of layers n1, and
the second length L2 (μm) is equal to the first length L1 (μm).

### Claim 10 (depends on 6)

The optical transmission apparatus according to claim 6, wherein the second semiconductor optical amplifier is controlled to operate in a gain saturation region of the second semiconductor optical amplifier.

### Claim 11 (depends on 6)

The optical transmission apparatus according to claim 6, further comprising a semiconductor laser to output light to the optical input portion, wherein
the first multilevel optical phase modulator, the first semiconductor optical amplifier, the optical demultiplexer, and the semiconductor laser are formed on a single semiconductor substrate.