[Python] Power Spectral Density of Sinusoid in Python using Scipy

I have the following code to generate a sinusoidal signal with some noise floor:

Kmax = 1000000
fref = 125e6
fin = fref/5
t = 10*np.linspace(0,Kmax,Kmax)/fref

tdelay = (1+np.sin(2*np.pi*fin*t)) + np.random.uniform(0,0.2,Kmax)
plt.plot(t,tdelay)
plt.grid()
plt.show()
f, psd_td = signal.welch((tdelay - np.mean(tdelay)), fref, nperseg = len(tdelay) / 8)
plt.semilogx(f,10*np.log10(psd_td), label = 'PSD Signal')
plt.grid()
plt.show()


The time domain waveform looks as below:

But the Power spectral density does not show me the signal tone:

Could someone explain what am I doing wrong? And why I do not observe the signal tone.

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